diff --git a/stdlib/CMakeLists.txt b/stdlib/CMakeLists.txt
index a2e5f71c3da43..3fa2f27217573 100644
--- a/stdlib/CMakeLists.txt
+++ b/stdlib/CMakeLists.txt
@@ -102,6 +102,10 @@ set(SWIFT_STDLIB_ENABLE_LTO OFF CACHE STRING "Build Swift stdlib with LTO. One
     must specify the form of LTO by setting this to one of: 'full', 'thin'. This
     option only affects the standard library and runtime, not tools.")
 
+option(SWIFT_ENABLE_REFLECTION
+  "Build stdlib with support for runtime reflection and mirrors."
+  TRUE)
+
 #
 # End of user-configurable options.
 #
diff --git a/stdlib/cmake/modules/AddSwiftStdlib.cmake b/stdlib/cmake/modules/AddSwiftStdlib.cmake
index 4d8a588a5d4e6..492c9864f0dc7 100644
--- a/stdlib/cmake/modules/AddSwiftStdlib.cmake
+++ b/stdlib/cmake/modules/AddSwiftStdlib.cmake
@@ -315,6 +315,10 @@ function(_add_target_variant_c_compile_flags)
     list(APPEND result "-DSWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES")
   endif()
 
+  if(SWIFT_ENABLE_REFLECTION)
+    list(APPEND result "-DSWIFT_ENABLE_REFLECTION")
+  endif()
+
   if(SWIFT_RUNTIME_MACHO_NO_DYLD)
     list(APPEND result "-DSWIFT_RUNTIME_MACHO_NO_DYLD")
   endif()
diff --git a/stdlib/cmake/modules/SwiftSource.cmake b/stdlib/cmake/modules/SwiftSource.cmake
index 9ca753c1ac909..c21a99c10307d 100644
--- a/stdlib/cmake/modules/SwiftSource.cmake
+++ b/stdlib/cmake/modules/SwiftSource.cmake
@@ -432,6 +432,12 @@ function(_compile_swift_files
     list(APPEND swift_flags "-Xfrontend" "-emit-sorted-sil")
   endif()
 
+  if(NOT SWIFT_ENABLE_REFLECTION)
+    list(APPEND swift_flags "-Xfrontend" "-disable-reflection-metadata")
+  else()
+    list(APPEND swift_flags "-D" "SWIFT_ENABLE_REFLECTION")
+  endif()
+
   # FIXME: Cleaner way to do this?
   if(SWIFTFILE_IS_STDLIB_CORE)
     list(APPEND swift_flags
diff --git a/stdlib/public/core/AnyHashable.swift b/stdlib/public/core/AnyHashable.swift
index 21ee82f4dc481..3225dc5f2e1d3 100644
--- a/stdlib/public/core/AnyHashable.swift
+++ b/stdlib/public/core/AnyHashable.swift
@@ -252,6 +252,7 @@ extension AnyHashable: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension AnyHashable: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
@@ -259,6 +260,7 @@ extension AnyHashable: CustomReflectable {
       children: ["value": base])
   }
 }
+#endif
 
 @available(macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0, *)
 extension AnyHashable: _HasCustomAnyHashableRepresentation {
diff --git a/stdlib/public/core/Array.swift b/stdlib/public/core/Array.swift
index 5fb18d7ea6d75..5ad228816394e 100644
--- a/stdlib/public/core/Array.swift
+++ b/stdlib/public/core/Array.swift
@@ -1414,6 +1414,7 @@ extension Array {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Array: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1423,6 +1424,7 @@ extension Array: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension Array: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.
diff --git a/stdlib/public/core/ArraySlice.swift b/stdlib/public/core/ArraySlice.swift
index d797b0223a505..07e8a0f6b7c45 100644
--- a/stdlib/public/core/ArraySlice.swift
+++ b/stdlib/public/core/ArraySlice.swift
@@ -1118,6 +1118,7 @@ extension ArraySlice: RangeReplaceableCollection {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ArraySlice: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1127,6 +1128,7 @@ extension ArraySlice: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension ArraySlice: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.
diff --git a/stdlib/public/core/ClosedRange.swift b/stdlib/public/core/ClosedRange.swift
index 0ff48522689c6..079ae8fad6386 100644
--- a/stdlib/public/core/ClosedRange.swift
+++ b/stdlib/public/core/ClosedRange.swift
@@ -396,12 +396,14 @@ extension ClosedRange: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ClosedRange: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
       self, children: ["lowerBound": lowerBound, "upperBound": upperBound])
   }
 }
+#endif
 
 extension ClosedRange {
   /// Returns a copy of this range clamped to the given limiting range.
diff --git a/stdlib/public/core/CollectionOfOne.swift b/stdlib/public/core/CollectionOfOne.swift
index 7bdd41928a1c8..04e2c3c2a9fef 100644
--- a/stdlib/public/core/CollectionOfOne.swift
+++ b/stdlib/public/core/CollectionOfOne.swift
@@ -165,11 +165,13 @@ extension CollectionOfOne: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension CollectionOfOne: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(self, children: ["element": _element])
   }
 }
+#endif
 
 extension CollectionOfOne: Sendable where Element: Sendable { }
 extension CollectionOfOne.Iterator: Sendable where Element: Sendable { }
diff --git a/stdlib/public/core/ContiguousArray.swift b/stdlib/public/core/ContiguousArray.swift
index 89dcec8c804f6..e3daceaf36244 100644
--- a/stdlib/public/core/ContiguousArray.swift
+++ b/stdlib/public/core/ContiguousArray.swift
@@ -1019,6 +1019,7 @@ extension ContiguousArray: RangeReplaceableCollection {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ContiguousArray: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1028,6 +1029,7 @@ extension ContiguousArray: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension ContiguousArray: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.
diff --git a/stdlib/public/core/DebuggerSupport.swift b/stdlib/public/core/DebuggerSupport.swift
index af1e130935184..ef9eafeab81f7 100644
--- a/stdlib/public/core/DebuggerSupport.swift
+++ b/stdlib/public/core/DebuggerSupport.swift
@@ -12,6 +12,8 @@
 
 import SwiftShims
 
+#if SWIFT_ENABLE_REFLECTION
+
 @frozen // namespace
 public enum _DebuggerSupport {
   private enum CollectionStatus {
@@ -262,6 +264,8 @@ public func _stringForPrintObject(_ value: Any) -> String {
   return _DebuggerSupport.stringForPrintObject(value)
 }
 
+#endif // SWIFT_ENABLE_REFLECTION
+
 public func _debuggerTestingCheckExpect(_: String, _: String) { }
 
 // Utilities to get refcount(s) of class objects.
diff --git a/stdlib/public/core/Dictionary.swift b/stdlib/public/core/Dictionary.swift
index 914e35b43f8fa..dcebf90dc72bf 100644
--- a/stdlib/public/core/Dictionary.swift
+++ b/stdlib/public/core/Dictionary.swift
@@ -2033,6 +2033,7 @@ extension Dictionary.Iterator: IteratorProtocol {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Dictionary.Iterator: CustomReflectable {
   /// A mirror that reflects the iterator.
   public var customMirror: Mirror {
@@ -2049,6 +2050,7 @@ extension Dictionary: CustomReflectable {
     return Mirror(self, unlabeledChildren: self, displayStyle: style)
   }
 }
+#endif
 
 extension Dictionary {
   /// Removes and returns the first key-value pair of the dictionary if the
diff --git a/stdlib/public/core/Dump.swift b/stdlib/public/core/Dump.swift
index 24651aad32936..4f33668a88626 100644
--- a/stdlib/public/core/Dump.swift
+++ b/stdlib/public/core/Dump.swift
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if SWIFT_ENABLE_REFLECTION
+
 /// Dumps the given object's contents using its mirror to the specified output
 /// stream.
 ///
@@ -247,3 +249,4 @@ internal func _dumpSuperclass_unlocked<TargetStream: TextOutputStream>(
   }
 }
 
+#endif // SWIFT_ENABLE_REFLECTION
diff --git a/stdlib/public/core/MigrationSupport.swift b/stdlib/public/core/MigrationSupport.swift
index c4dbf718825d4..9d934144440a4 100644
--- a/stdlib/public/core/MigrationSupport.swift
+++ b/stdlib/public/core/MigrationSupport.swift
@@ -309,12 +309,14 @@ extension Substring {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Substring: _CustomPlaygroundQuickLookable {
   @available(swift, deprecated: 4.2/*, obsoleted: 5.0*/, message: "Substring.customPlaygroundQuickLook will be removed in a future Swift version")
   public var customPlaygroundQuickLook: _PlaygroundQuickLook {
     return String(self).customPlaygroundQuickLook
   }
 }
+#endif
 
 extension Collection {
   // FIXME: <rdar://problem/34142121>
@@ -630,6 +632,7 @@ public enum _PlaygroundQuickLook {
   case _raw([UInt8], String)
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension _PlaygroundQuickLook {
   /// Creates a new Quick Look for the given instance.
   ///
@@ -663,6 +666,7 @@ extension _PlaygroundQuickLook {
     }
   }
 }
+#endif
 
 /// A type that explicitly supplies its own playground Quick Look.
 ///
diff --git a/stdlib/public/core/Mirror.swift b/stdlib/public/core/Mirror.swift
index f900aab4986ac..3a953e12e7c5b 100644
--- a/stdlib/public/core/Mirror.swift
+++ b/stdlib/public/core/Mirror.swift
@@ -12,6 +12,8 @@
 // FIXME: ExistentialCollection needs to be supported before this will work
 // without the ObjC Runtime.
 
+#if SWIFT_ENABLE_REFLECTION
+
 /// A representation of the substructure and display style of an instance of
 /// any type.
 ///
@@ -456,6 +458,70 @@ extension Mirror {
   }
 }
 
+#else  // SWIFT_ENABLE_REFLECTION
+
+@available(*, unavailable)
+public struct Mirror {
+  public enum AncestorRepresentation {
+    case generated
+    case customized(() -> Mirror)
+    case suppressed
+  }
+  public init(reflecting subject: Any) { Builtin.unreachable() }
+  public typealias Child = (label: String?, value: Any)
+  public typealias Children = AnyCollection<Child>
+  public enum DisplayStyle: Sendable {
+    case `struct`, `class`, `enum`, tuple, optional, collection
+    case dictionary, `set`
+  }
+  public init<Subject, C: Collection>(
+    _ subject: Subject,
+    children: C,
+    displayStyle: DisplayStyle? = nil,
+    ancestorRepresentation: AncestorRepresentation = .generated
+  ) where C.Element == Child { Builtin.unreachable() }
+  public init<Subject, C: Collection>(
+    _ subject: Subject,
+    unlabeledChildren: C,
+    displayStyle: DisplayStyle? = nil,
+    ancestorRepresentation: AncestorRepresentation = .generated
+  ) { Builtin.unreachable() }
+  public init<Subject>(
+    _ subject: Subject,
+    children: KeyValuePairs<String, Any>,
+    displayStyle: DisplayStyle? = nil,
+    ancestorRepresentation: AncestorRepresentation = .generated
+  ) { Builtin.unreachable() }
+  public let subjectType: Any.Type
+  public let children: Children
+  public let displayStyle: DisplayStyle?
+  public var superclassMirror: Mirror? { Builtin.unreachable() }
+}
+
+@available(*, unavailable)
+public protocol CustomReflectable {
+  var customMirror: Mirror { get }
+}
+
+@available(*, unavailable)
+public protocol CustomLeafReflectable: CustomReflectable {}
+
+@available(*, unavailable)
+public protocol MirrorPath {}
+@available(*, unavailable)
+extension Int: MirrorPath {}
+@available(*, unavailable)
+extension String: MirrorPath {}
+
+@available(*, unavailable)
+extension Mirror {
+  public func descendant(_ first: MirrorPath, _ rest: MirrorPath...) -> Any? {
+    Builtin.unreachable()
+  }
+}
+
+#endif  // SWIFT_ENABLE_REFLECTION
+
 //===--- General Utilities ------------------------------------------------===//
 
 extension String {
@@ -693,6 +759,8 @@ extension String {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
+
 /// Reflection for `Mirror` itself.
 extension Mirror: CustomStringConvertible {
   public var description: String {
@@ -705,3 +773,5 @@ extension Mirror: CustomReflectable {
     return Mirror(self, children: [:])
   }
 }
+
+#endif  // SWIFT_ENABLE_REFLECTION
diff --git a/stdlib/public/core/Mirrors.swift b/stdlib/public/core/Mirrors.swift
index 171adc99673f6..fd682555e494e 100644
--- a/stdlib/public/core/Mirrors.swift
+++ b/stdlib/public/core/Mirrors.swift
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if SWIFT_ENABLE_REFLECTION
+
 extension Float: CustomReflectable {
   /// A mirror that reflects the `Float` instance.
   public var customMirror: Mirror {
@@ -258,3 +260,5 @@ extension Float80: CustomReflectable {
   }
 }
 #endif
+
+#endif
diff --git a/stdlib/public/core/Optional.swift b/stdlib/public/core/Optional.swift
index bea036409826f..35dca316dc24b 100644
--- a/stdlib/public/core/Optional.swift
+++ b/stdlib/public/core/Optional.swift
@@ -279,6 +279,7 @@ extension Optional: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Optional: CustomReflectable {
   public var customMirror: Mirror {
     switch self {
@@ -292,6 +293,7 @@ extension Optional: CustomReflectable {
     }
   }
 }
+#endif
 
 @_transparent
 public // COMPILER_INTRINSIC
diff --git a/stdlib/public/core/OutputStream.swift b/stdlib/public/core/OutputStream.swift
index 5ede1f939ea20..c5d357f8c6488 100644
--- a/stdlib/public/core/OutputStream.swift
+++ b/stdlib/public/core/OutputStream.swift
@@ -296,6 +296,7 @@ internal func _fallbackEnumRawValue<T>(_ value: T) -> Int64? {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 /// Do our best to print a value that cannot be printed directly.
 @_semantics("optimize.sil.specialize.generic.never")
 internal func _adHocPrint_unlocked<T, TargetStream: TextOutputStream>(
@@ -396,6 +397,7 @@ internal func _adHocPrint_unlocked<T, TargetStream: TextOutputStream>(
     }
   }
 }
+#endif
 
 @usableFromInline
 @_semantics("optimize.sil.specialize.generic.never")
@@ -435,8 +437,12 @@ internal func _print_unlocked<T, TargetStream: TextOutputStream>(
     return
   }
 
+#if SWIFT_ENABLE_REFLECTION
   let mirror = Mirror(reflecting: value)
   _adHocPrint_unlocked(value, mirror, &target, isDebugPrint: false)
+#else
+  target.write("(value cannot be printed without reflection)")
+#endif
 }
 
 //===----------------------------------------------------------------------===//
@@ -463,10 +469,15 @@ public func _debugPrint_unlocked<T, TargetStream: TextOutputStream>(
     return
   }
 
+#if SWIFT_ENABLE_REFLECTION
   let mirror = Mirror(reflecting: value)
   _adHocPrint_unlocked(value, mirror, &target, isDebugPrint: true)
+#else
+  target.write("(value cannot be printed without reflection)")
+#endif
 }
 
+#if SWIFT_ENABLE_REFLECTION
 @_semantics("optimize.sil.specialize.generic.never")
 internal func _dumpPrint_unlocked<T, TargetStream: TextOutputStream>(
     _ value: T, _ mirror: Mirror, _ target: inout TargetStream
@@ -533,6 +544,7 @@ internal func _dumpPrint_unlocked<T, TargetStream: TextOutputStream>(
 
   _adHocPrint_unlocked(value, mirror, &target, isDebugPrint: true)
 }
+#endif
 
 //===----------------------------------------------------------------------===//
 // OutputStreams
diff --git a/stdlib/public/core/Pointer.swift b/stdlib/public/core/Pointer.swift
index f248b4799a9cd..6b59eb16ba4d6 100644
--- a/stdlib/public/core/Pointer.swift
+++ b/stdlib/public/core/Pointer.swift
@@ -10,11 +10,17 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if SWIFT_ENABLE_REFLECTION
+public typealias _CustomReflectableOrNone = CustomReflectable
+#else
+public typealias _CustomReflectableOrNone = Any
+#endif
+
 /// A stdlib-internal protocol modeled by the intrinsic pointer types,
 /// UnsafeMutablePointer, UnsafePointer, UnsafeRawPointer,
 /// UnsafeMutableRawPointer, and AutoreleasingUnsafeMutablePointer.
 public protocol _Pointer
-: Hashable, Strideable, CustomDebugStringConvertible, CustomReflectable {
+: Hashable, Strideable, CustomDebugStringConvertible, _CustomReflectableOrNone {
   /// A type that represents the distance between two pointers.
   typealias Distance = Int
   
@@ -220,6 +226,7 @@ extension _Pointer /*: CustomDebugStringConvertible */ {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension _Pointer /*: CustomReflectable */ {
   public var customMirror: Mirror {
     let ptrValue = UInt64(
@@ -227,6 +234,7 @@ extension _Pointer /*: CustomReflectable */ {
     return Mirror(self, children: ["pointerValue": ptrValue])
   }
 }
+#endif
 
 extension Int {
   /// Creates a new value with the bit pattern of the given pointer.
diff --git a/stdlib/public/core/Prespecialize.swift b/stdlib/public/core/Prespecialize.swift
index b4dd39d553a68..f8e2f735f1390 100644
--- a/stdlib/public/core/Prespecialize.swift
+++ b/stdlib/public/core/Prespecialize.swift
@@ -83,7 +83,9 @@ internal func _prespecialize() {
   consume(Optional<CodingKey>.self)
   consume(Optional<CodingUserInfoKey>.self)
   consume(Optional<CustomDebugStringConvertible>.self)
+#if SWIFT_ENABLE_REFLECTION
   consume(Optional<CustomReflectable>.self)
+#endif
   consume(Optional<CustomStringConvertible>.self)
   consume(Optional<Dictionary<AnyHashable, Any>>.self)
   consume(Optional<Dictionary<String, Any>>.self)
@@ -93,7 +95,9 @@ internal func _prespecialize() {
   consume(Optional<Double>.self)
   consume(Optional<Int64>.self)
   consume(Optional<Int8>.self)
+#if SWIFT_ENABLE_REFLECTION
   consume(Optional<Mirror.DisplayStyle>.self)
+#endif
   consume(Optional<Optional<Int64>>.self)
   consume(Optional<Optional<String>>.self)
   consume(Optional<Set<String>>.self)
diff --git a/stdlib/public/core/Range.swift b/stdlib/public/core/Range.swift
index fde006d0037b1..2c09a510c2779 100644
--- a/stdlib/public/core/Range.swift
+++ b/stdlib/public/core/Range.swift
@@ -388,12 +388,14 @@ extension Range: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Range: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
       self, children: ["lowerBound": lowerBound, "upperBound": upperBound])
   }
 }
+#endif
 
 extension Range: Equatable {
   /// Returns a Boolean value indicating whether two ranges are equal.
diff --git a/stdlib/public/core/ReflectionMirror.swift b/stdlib/public/core/ReflectionMirror.swift
index 2f68b9078aa21..91cf84b1f8170 100644
--- a/stdlib/public/core/ReflectionMirror.swift
+++ b/stdlib/public/core/ReflectionMirror.swift
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if SWIFT_ENABLE_REFLECTION
+
 import SwiftShims
 
 @_silgen_name("swift_isClassType")
@@ -365,3 +367,5 @@ public func _forEachFieldWithKeyPath<Root>(
 
   return true
 }
+
+#endif
diff --git a/stdlib/public/core/Set.swift b/stdlib/public/core/Set.swift
index 91a67b3d15f2e..f4fb463fe24db 100644
--- a/stdlib/public/core/Set.swift
+++ b/stdlib/public/core/Set.swift
@@ -1572,6 +1572,7 @@ extension Set.Iterator: IteratorProtocol {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Set.Iterator: CustomReflectable {
   /// A mirror that reflects the iterator.
   public var customMirror: Mirror {
@@ -1588,6 +1589,7 @@ extension Set: CustomReflectable {
     return Mirror(self, unlabeledChildren: self, displayStyle: style)
   }
 }
+#endif
 
 extension Set {
   /// Removes and returns the first element of the set.
diff --git a/stdlib/public/core/StaticString.swift b/stdlib/public/core/StaticString.swift
index 086c6b3c86085..ac114c755a26f 100644
--- a/stdlib/public/core/StaticString.swift
+++ b/stdlib/public/core/StaticString.swift
@@ -308,9 +308,11 @@ extension StaticString: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension StaticString: CustomReflectable {
 
   public var customMirror: Mirror {
     return Mirror(reflecting: description)
   }
 }
+#endif
diff --git a/stdlib/public/core/Stride.swift b/stdlib/public/core/Stride.swift
index e9a43bbb4fb3f..d17fbf4239dfc 100644
--- a/stdlib/public/core/Stride.swift
+++ b/stdlib/public/core/Stride.swift
@@ -386,11 +386,13 @@ extension StrideTo: Sequence {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension StrideTo: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(self, children: ["from": _start, "to": _end, "by": _stride])
   }
 }
+#endif
 
 // FIXME(conditional-conformances): This does not yet compile (SR-6474).
 #if false
@@ -597,12 +599,14 @@ extension StrideThrough: Sequence {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension StrideThrough: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(self,
       children: ["from": _start, "through": _end, "by": _stride])
   }
 }
+#endif
 
 // FIXME(conditional-conformances): This does not yet compile (SR-6474).
 #if false
diff --git a/stdlib/public/core/StringUTF16View.swift b/stdlib/public/core/StringUTF16View.swift
index 555137789d452..5f19b2823a40a 100644
--- a/stdlib/public/core/StringUTF16View.swift
+++ b/stdlib/public/core/StringUTF16View.swift
@@ -405,6 +405,7 @@ extension String.UTF16View.Index {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 // Reflection
 extension String.UTF16View: CustomReflectable {
   /// Returns a mirror that reflects the UTF-16 view of a string.
@@ -412,6 +413,7 @@ extension String.UTF16View: CustomReflectable {
     return Mirror(self, unlabeledChildren: self)
   }
 }
+#endif
 
 // Slicing
 extension String.UTF16View {
diff --git a/stdlib/public/core/StringUTF8View.swift b/stdlib/public/core/StringUTF8View.swift
index b0d8f7c1170ad..3883db5f8491e 100644
--- a/stdlib/public/core/StringUTF8View.swift
+++ b/stdlib/public/core/StringUTF8View.swift
@@ -346,6 +346,7 @@ extension String.UTF8View.Index {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 // Reflection
 extension String.UTF8View: CustomReflectable {
   /// Returns a mirror that reflects the UTF-8 view of a string.
@@ -353,6 +354,7 @@ extension String.UTF8View: CustomReflectable {
     return Mirror(self, unlabeledChildren: self)
   }
 }
+#endif
 
 //===--- Slicing Support --------------------------------------------------===//
 /// In Swift 3.2, in the absence of type context,
diff --git a/stdlib/public/core/StringUnicodeScalarView.swift b/stdlib/public/core/StringUnicodeScalarView.swift
index 8a0ae258371fe..6c6a0c8fa3d8c 100644
--- a/stdlib/public/core/StringUnicodeScalarView.swift
+++ b/stdlib/public/core/StringUnicodeScalarView.swift
@@ -382,6 +382,7 @@ extension String.UnicodeScalarIndex {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 // Reflection
 extension String.UnicodeScalarView: CustomReflectable {
   /// Returns a mirror that reflects the Unicode scalars view of a string.
@@ -389,7 +390,7 @@ extension String.UnicodeScalarView: CustomReflectable {
     return Mirror(self, unlabeledChildren: self)
   }
 }
-
+#endif
 
 //===--- Slicing Support --------------------------------------------------===//
 /// In Swift 3.2, in the absence of type context,
diff --git a/stdlib/public/core/Substring.swift b/stdlib/public/core/Substring.swift
index 1b414b2d9710d..d0ae836ffea88 100644
--- a/stdlib/public/core/Substring.swift
+++ b/stdlib/public/core/Substring.swift
@@ -307,9 +307,11 @@ extension Substring: StringProtocol {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Substring: CustomReflectable {
  public var customMirror: Mirror { return String(self).customMirror }
 }
+#endif
 
 extension Substring: CustomStringConvertible {
   @inlinable @inline(__always)
diff --git a/stdlib/public/runtime/ReflectionMirror.cpp b/stdlib/public/runtime/ReflectionMirror.cpp
index 141da5ff01dec..5158894ffd54a 100644
--- a/stdlib/public/runtime/ReflectionMirror.cpp
+++ b/stdlib/public/runtime/ReflectionMirror.cpp
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifdef SWIFT_ENABLE_REFLECTION
+
 #include "swift/Basic/Lazy.h"
 #include "swift/Runtime/Reflection.h"
 #include "swift/Runtime/Casting.h"
@@ -1106,3 +1108,5 @@ id swift_reflectionMirror_quickLookObject(OpaqueValue *value, const Metadata *T)
   return call(value, T, nullptr, [](ReflectionMirrorImpl *impl) { return impl->quickLookObject(); });
 }
 #endif
+
+#endif  // SWIFT_ENABLE_REFLECTION
diff --git a/stdlib/public/runtime/ReflectionMirrorObjC.mm b/stdlib/public/runtime/ReflectionMirrorObjC.mm
index a9efbe107b35d..52d15d6771d53 100644
--- a/stdlib/public/runtime/ReflectionMirrorObjC.mm
+++ b/stdlib/public/runtime/ReflectionMirrorObjC.mm
@@ -12,7 +12,7 @@
 
 #include "swift/Runtime/Config.h"
 
-#if SWIFT_OBJC_INTEROP
+#if SWIFT_OBJC_INTEROP && defined(SWIFT_ENABLE_REFLECTION)
 
 #include "Private.h"
 #include <Foundation/Foundation.h>
diff --git a/utils/build-presets.ini b/utils/build-presets.ini
index 529f771da99d7..fbe67d4b691a1 100644
--- a/utils/build-presets.ini
+++ b/utils/build-presets.ini
@@ -2451,6 +2451,7 @@ build-swift-dynamic-stdlib=0
 build-swift-static-stdlib=1
 swift-objc-interop=0
 swift-enable-compatibility-overrides=0
+swift-enable-reflection=1
 swift-runtime-macho-no-dyld=1
 swift-stdlib-has-darwin-libmalloc=0
 swift-stdlib-single-threaded-runtime=1
diff --git a/utils/build-script-impl b/utils/build-script-impl
index 70e7375fccccd..8f72fba02e8c0 100755
--- a/utils/build-script-impl
+++ b/utils/build-script-impl
@@ -204,6 +204,7 @@ KNOWN_SETTINGS=(
     stdlib-deployment-targets                     ""                "space-separated list of targets to configure the Swift standard library to be compiled or cross-compiled for"
     swift-objc-interop                            ""                "whether to enable interoperability with Objective-C, default is 1 on Apple platfors, 0 otherwise"
     swift-enable-compatibility-overrides          "1"               "whether to support back-deploying compatibility fixes for newer apps running on older runtimes"
+    swift-enable-reflection                       "1"               "whether to support reflection and mirrors"
     swift-runtime-macho-no-dyld                   "0"               "whether to build stdlib assuming the runtime environment does not support dynamic modules"
     swift-stdlib-single-threaded-runtime          "0"               "whether to build stdlib as a single-threaded runtime only"
     swift-stdlib-os-versioning                    "1"               "whether to build stdlib with availability based on OS versions (Darwin only)"
@@ -2053,6 +2054,13 @@ for host in "${ALL_HOSTS[@]}"; do
                     )
                 fi
 
+                if [[ "${SWIFT_ENABLE_REFLECTION}" == "0" ]] ; then
+                    cmake_options=(
+                        "${cmake_options[@]}"
+                        -DSWIFT_ENABLE_REFLECTION:BOOL=FALSE
+                    )
+                fi
+
                 if [[ "${SWIFT_PRIMARY_VARIANT_SDK}" ]] ; then
                     cmake_options=(
                         "${cmake_options[@]}"