diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -1043,6 +1043,13 @@
       // contrast, EH frames are handled like regular ConcatInputSections.)
       if (section->name == section_names::compactUnwind)
         continue;
+
+      if (section->name == section_names::objcImageInfo) {
+        assert(section->subsections.size() == 1);
+        in.objCImageInfo->addInput(section->subsections[0].isec);
+        continue;
+      }
+
       ConcatOutputSection *osec = nullptr;
       for (const Subsection &subsection : section->subsections) {
         if (auto *isec = dyn_cast<ConcatInputSection>(subsection.isec)) {
diff --git a/lld/MachO/SyntheticSections.h b/lld/MachO/SyntheticSections.h
--- a/lld/MachO/SyntheticSections.h
+++ b/lld/MachO/SyntheticSections.h
@@ -19,6 +19,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Hashing.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/MathExtras.h"
@@ -600,6 +601,23 @@
   std::unordered_map<uint32_t, uint64_t> literal4Map;
 };
 
+class ObjCImageInfoSection final : public SyntheticSection {
+public:
+  ObjCImageInfoSection();
+  uint64_t getSize() const override { return 8; }
+  void addInput(const InputSection *isec) { inputs.push_back(isec); }
+  void finalizeContents();
+  void writeTo(uint8_t *buf) const override;
+
+private:
+  struct ImageInfo {
+    uint8_t swiftVersion;
+    bool hasCategoryClassProperties = true;
+  } info;
+  static llvm::Optional<ImageInfo> parseImageInfo(const InputSection *isec);
+  std::vector<const InputSection *> inputs;
+};
+
 struct InStruct {
   const uint8_t *bufferStart = nullptr;
   MachHeaderSection *header = nullptr;
@@ -616,6 +634,7 @@
   StubsSection *stubs = nullptr;
   StubHelperSection *stubHelper = nullptr;
   UnwindInfoSection *unwindInfo = nullptr;
+  ObjCImageInfoSection *objCImageInfo = nullptr;
   ConcatInputSection *imageLoaderCache = nullptr;
 };
 
diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp
--- a/lld/MachO/SyntheticSections.cpp
+++ b/lld/MachO/SyntheticSections.cpp
@@ -1574,6 +1574,102 @@
     memcpy(buf + p.second * 4, &p.first, 4);
 }
 
+ObjCImageInfoSection::ObjCImageInfoSection()
+    : SyntheticSection(segment_names::data, section_names::objcImageInfo) {}
+
+Optional<ObjCImageInfoSection::ImageInfo>
+ObjCImageInfoSection::parseImageInfo(const InputSection *isec) {
+  Optional<ImageInfo> info;
+  ArrayRef<uint8_t> data = isec->data;
+  // The image info struct has the following layout:
+  // struct {
+  //   uint32_t version;
+  //   uint32_t flags;
+  // };
+  if (data.size() != 8) {
+    warn(toString(isec->getFile()) + ": invalid __objc_imageinfo size");
+    return info;
+  }
+
+  auto *buf = reinterpret_cast<const uint32_t *>(data.data());
+  if (read32le(buf) != 0) {
+    warn(toString(isec->getFile()) + ": invalid __objc_imageinfo version");
+    return info;
+  }
+
+  info = ImageInfo{};
+  uint32_t flags = read32le(buf + 1);
+  info->swiftVersion = (flags >> 8) & 0xff;
+  info->hasCategoryClassProperties = flags & 0x40;
+  return info;
+}
+
+static std::string swiftVersionString(uint8_t version) {
+  switch (version) {
+    case 1:
+      return "1.0";
+    case 2:
+      return "1.1";
+    case 3:
+      return "2.0";
+    case 4:
+      return "3.0";
+    case 5:
+      return "4.0";
+    default:
+      return ("0x" + Twine::utohexstr(version)).str();
+  }
+}
+
+// Validate each object file's __objc_imageinfo and use them to generate the
+// image info for the output binary. Only two pieces of info are relevant:
+// 1. The Swift version (should be identical across inputs)
+// 2. `bool hasCategoryClassProperties` (true only if true for all inputs)
+void ObjCImageInfoSection::finalizeContents() {
+  if (inputs.size() == 0)
+    return;
+
+  // Find the first valid image info sequentially so that any error messages
+  // we generate are deterministic.
+  auto it = inputs.begin();
+  InputFile *firstFile;
+  for (; it != inputs.end(); ++it) {
+    if (Optional<ImageInfo> inputInfo = parseImageInfo(*it)) {
+      info.swiftVersion = inputInfo->swiftVersion;
+      info.hasCategoryClassProperties &= inputInfo->hasCategoryClassProperties;
+      firstFile = (*it)->getFile();
+      break;
+    } else {
+      // Invalid image infos should be treated has having
+      // hasCategoryClassProperties = false;
+      info.hasCategoryClassProperties = false;
+    }
+  }
+
+  parallelForEach(it, inputs.end(), [&](const InputSection *isec) {
+    Optional<ImageInfo> inputInfo = parseImageInfo(isec);
+    if (!inputInfo) {
+      info.hasCategoryClassProperties = false;
+      return;
+    }
+
+    if (!inputInfo->hasCategoryClassProperties)
+      info.hasCategoryClassProperties = false;
+
+    if (info.swiftVersion != inputInfo->swiftVersion)
+      error("Swift version mismatch: " + toString(firstFile) + " has version " +
+            swiftVersionString(info.swiftVersion) + " but " +
+            toString(isec->getFile()) + " has version " +
+            swiftVersionString(inputInfo->swiftVersion));
+  });
+}
+
+void ObjCImageInfoSection::writeTo(uint8_t *buf) const {
+  uint32_t flags = info.hasCategoryClassProperties ? 0x40 : 0x0;
+  flags |= info.swiftVersion << 8;
+  write32le(buf + 4, flags);
+}
+
 void macho::createSyntheticSymbols() {
   auto addHeaderSymbol = [](const char *name) {
     symtab->addSynthetic(name, in.header->isec, /*value=*/0,
diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -996,7 +996,7 @@
       if (!osec->isNeeded())
         continue;
       // Other kinds of OutputSections have already been finalized.
-      if (auto concatOsec = dyn_cast<ConcatOutputSection>(osec))
+      if (auto *concatOsec = dyn_cast<ConcatOutputSection>(osec))
         concatOsec->finalizeContents();
     }
   }
@@ -1164,6 +1164,10 @@
 
   if (in.stubHelper->isNeeded())
     in.stubHelper->setup();
+
+  if (in.objCImageInfo->isNeeded())
+    in.objCImageInfo->finalizeContents();
+
   // At this point, we should know exactly which output sections are needed,
   // courtesy of scanSymbols() and scanRelocations().
   createOutputSections<LP>();
@@ -1210,6 +1214,7 @@
   in.stubs = make<StubsSection>();
   in.stubHelper = make<StubHelperSection>();
   in.unwindInfo = makeUnwindInfoSection();
+  in.objCImageInfo = make<ObjCImageInfoSection>();
 
   // This section contains space for just a single word, and will be used by
   // dyld to cache an address to the image loader it uses.
diff --git a/lld/test/MachO/objc-imageinfo.s b/lld/test/MachO/objc-imageinfo.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/objc-imageinfo.s
@@ -0,0 +1,136 @@
+# REQUIRES: x86
+
+# RUN: rm -rf %t; split-file %s %t
+
+## ld64 ignores the __objc_imageinfo section entirely if there is no actual
+## ObjC class + category data in the file. LLD doesn't yet do this check, but
+## to make this test work for both linkers, I am inserting an appropriate class
+## definition into each test file.
+# RUN: cat %t/objc-no-category-cls.s   %t/foo-cls.s > %t/objc-no-category-cls-1.s
+# RUN: cat %t/objc-with-category-cls.s %t/foo-cls.s > %t/objc-with-category-cls-1.s
+# RUN: cat %t/objc-ignored-flags.s     %t/foo-cls.s > %t/objc-ignored-flags-1.s
+# RUN: cat %t/objc-invalid-version.s   %t/foo-cls.s > %t/objc-invalid-version-1.s
+# RUN: cat %t/swift-version-1.s        %t/foo-cls.s > %t/swift-version-1-1.s
+# RUN: cat %t/swift-version-2.s        %t/foo-cls.s > %t/swift-version-2-1.s
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/objc-no-category-cls-1.s   -o %t/objc-no-category-cls.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/objc-with-category-cls-1.s -o %t/objc-with-category-cls.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/objc-ignored-flags-1.s     -o %t/objc-ignored-flags.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/objc-invalid-version-1.s   -o %t/objc-invalid-version.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/swift-version-1-1.s        -o %t/swift-version-1.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/swift-version-2-1.s        -o %t/swift-version-2.o
+
+# RUN: %lld -dylib -lSystem %t/objc-with-category-cls.o -o %t/test-with-cat
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" \
+# RUN:   %t/test-with-cat | FileCheck %s --check-prefix=HAS-CAT-CLS
+
+# RUN: %lld -dylib -lSystem %t/objc-no-category-cls.o -o %t/test-no-cat
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" \
+# RUN:   %t/test-no-cat | FileCheck %s --check-prefix=NO-CAT-CLS
+
+# RUN: %lld -dylib -lSystem %t/objc-no-category-cls.o %t/objc-with-category-cls.o -o %t/test1
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" %t/test1 \
+# RUN:   | FileCheck %s --check-prefix=NO-CAT-CLS
+
+# RUN: %lld -dylib -lSystem %t/objc-with-category-cls.o %t/objc-ignored-flags.o -o %t/test2
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" %t/test2 \
+# RUN:   | FileCheck %s --check-prefix=HAS-CAT-CLS
+
+# RUN: %lld -dylib -lSystem %t/objc-no-category-cls.o %t/objc-ignored-flags.o -o %t/test3
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" %t/test3 \
+# RUN:   | FileCheck %s --check-prefix=NO-CAT-CLS
+
+# RUN: %no-fatal-warnings-lld -dylib -lSystem %t/objc-with-category-cls.o \
+# RUN:   %t/objc-invalid-version.o -o %t/test4 2>&1 | FileCheck %s \
+# RUN:   --check-prefix=IMAGE-VERSION
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" %t/test4 \
+# RUN:   | FileCheck %s --check-prefix=NO-CAT-CLS
+
+# RUN: %no-fatal-warnings-lld -dylib -lSystem %t/objc-no-category-cls.o \
+# RUN:   %t/objc-invalid-version.o -o %t/test5 2>&1 | FileCheck %s \
+# RUN:   --check-prefix=IMAGE-VERSION
+# RUN: llvm-objdump --macho --section="__DATA_CONST,__objc_imageinfo" %t/test5 \
+# RUN:   | FileCheck %s --check-prefix=NO-CAT-CLS
+
+# RUN: not %lld -dylib -lSystem %t/swift-version-1.o %t/swift-version-2.o -o \
+# RUN:   /dev/null 2>&1 | FileCheck %s --check-prefix=SWIFT-MISMATCH-12
+# RUN: not %lld -dylib -lSystem %t/swift-version-2.o %t/swift-version-1.o -o \
+# RUN:   /dev/null 2>&1 | FileCheck %s --check-prefix=SWIFT-MISMATCH-21
+
+# HAS-CAT-CLS:       Contents of (__DATA_CONST,__objc_imageinfo) section
+# HAS-CAT-CLS:       00 00 00 40 00 00 00
+# HAS-CAT-CLS-EMPTY:
+
+# NO-CAT-CLS:       Contents of (__DATA_CONST,__objc_imageinfo) section
+# NO-CAT-CLS:       00 00 00 00 00 00 00
+# NO-CAT-CLS-EMPTY:
+
+# IMAGE-VERSION: warning: {{.*}}objc-invalid-version.o: invalid __objc_imageinfo version
+
+# SWIFT-MISMATCH-12: error: Swift version mismatch: {{.*}}swift-version-1.o has version 1.0 but {{.*}}swift-version-2.o has version 1.1
+# SWIFT-MISMATCH-21: error: Swift version mismatch: {{.*}}swift-version-2.o has version 1.1 but {{.*}}swift-version-1.o has version 1.0
+
+#--- objc-no-category-cls.s
+.section __DATA,__objc_imageinfo,regular,no_dead_strip
+.long 0
+.long 0
+
+#--- objc-with-category-cls.s
+.section __DATA,__objc_imageinfo,regular,no_dead_strip
+.long 0
+.long 0x40 ## "has category class properties" flag
+
+#--- objc-ignored-flags.s
+.section __DATA,__objc_imageinfo,regular,no_dead_strip
+.long 0
+## Only the 0x40 flag is carried through to the output binary.
+.long (0x40 | 0x20 | 0x4 | 0x2)
+
+#--- objc-invalid-version.s
+.section __DATA,__objc_imageinfo,regular,no_dead_strip
+.long 1 ## only 0 is valid; the flag field below will not be parsed.
+.long 0x40
+
+#--- swift-version-1.s
+.section __DATA,__objc_imageinfo,regular,no_dead_strip
+.long 0
+.byte 0x40
+.byte 0x1 ## Swift version
+.short 0
+
+#--- swift-version-2.s
+.section __DATA,__objc_imageinfo,regular,no_dead_strip
+.long 0
+.byte 0x40
+.byte 0x2 ## Swift version
+.short 0
+
+#--- foo-cls.s
+.section __TEXT,__objc_classname,cstring_literals
+L_CAT_NAME:
+.asciz "barcat"
+
+.section __DATA,__objc_data
+.p2align 3
+_OBJC_CLASS_$_FooClass:
+.space 40
+
+.section __DATA,__objc_const
+.p2align 3
+__OBJC_$_CATEGORY_INSTANCE_METHODS_FooClass_$_barcat:
+
+.p2align 3
+__OBJC_$_CATEGORY_FooClass_$_barcat:
+.quad L_CAT_NAME
+.quad _OBJC_CLASS_$_FooClass
+.quad __OBJC_$_CATEGORY_INSTANCE_METHODS_FooClass_$_barcat
+.quad 0
+.quad 0
+.quad 0
+.quad 0
+.long 64
+.space 4
+
+.section __DATA,__objc_catlist,regular,no_dead_strip
+.p2align 3
+.quad __OBJC_$_CATEGORY_FooClass_$_barcat