diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -26,6 +26,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/BinaryFormat/Magic.h"
+#include "llvm/Object/Archive.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -104,6 +105,17 @@
   MemoryBufferRef mbref = *buffer;
 
   switch (identify_magic(mbref.getBuffer())) {
+  case file_magic::archive: {
+    std::unique_ptr<object::Archive> file = CHECK(
+        object::Archive::create(mbref), path + ": failed to parse archive");
+
+    if (!file->isEmpty() && !file->hasSymbolTable()) {
+      error(mbref.getBufferIdentifier() +
+            ": archive has no index; run ranlib to add one");
+    }
+    inputFiles.push_back(make<ArchiveFile>(file.release()));
+    break;
+  }
   case file_magic::macho_object:
     inputFiles.push_back(make<ObjFile>(mbref));
     break;
diff --git a/lld/MachO/InputFiles.h b/lld/MachO/InputFiles.h
--- a/lld/MachO/InputFiles.h
+++ b/lld/MachO/InputFiles.h
@@ -28,6 +28,7 @@
   enum Kind {
     ObjKind,
     DylibKind,
+    ArchiveKind,
   };
 
   virtual ~InputFile() = default;
@@ -67,6 +68,17 @@
   uint64_t ordinal = 0; // Ordinal numbering starts from 1, so 0 is a sentinel
 };
 
+// .a file
+class ArchiveFile : public InputFile {
+public:
+  explicit ArchiveFile(llvm::object::Archive *file);
+  static bool classof(const InputFile *f) { return f->kind() == ArchiveKind; }
+  InputFile *fetch(const llvm::object::Archive::Symbol &sym);
+
+private:
+  llvm::DenseSet<uint64_t> seen;
+};
+
 extern std::vector<InputFile *> inputFiles;
 
 llvm::Optional<MemoryBufferRef> readFile(StringRef path);
diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -263,6 +263,31 @@
   }
 }
 
+ArchiveFile::ArchiveFile(llvm::object::Archive *f)
+    : InputFile(ArchiveKind, f->getMemoryBufferRef()) {
+  for (const object::Archive::Symbol &sym : f->symbols())
+    symtab->addLazy(sym.getName(), this, sym);
+}
+
+InputFile *ArchiveFile::fetch(const object::Archive::Symbol &sym) {
+  object::Archive::Child c =
+      CHECK(sym.getMember(), toString(this) +
+                                 ": could not get the member for symbol " +
+                                 sym.getName());
+
+  if (!seen.insert(c.getChildOffset()).second)
+    return nullptr;
+
+  MemoryBufferRef mb =
+      CHECK(c.getMemoryBufferRef(),
+            toString(this) +
+                ": could not get the buffer for the member defining symbol " +
+                sym.getName());
+  auto file = make<ObjFile>(mb);
+  sections.insert(sections.end(), file->sections.begin(), file->sections.end());
+  return file;
+}
+
 // Returns "<internal>" or "baz.o".
 std::string lld::toString(const InputFile *file) {
   return file ? std::string(file->getName()) : "<internal>";
diff --git a/lld/MachO/SymbolTable.h b/lld/MachO/SymbolTable.h
--- a/lld/MachO/SymbolTable.h
+++ b/lld/MachO/SymbolTable.h
@@ -30,6 +30,9 @@
 
   Symbol *addDylib(StringRef name, DylibFile *file);
 
+  Symbol *addLazy(StringRef name, ArchiveFile *file,
+                  const llvm::object::Archive::Symbol &sym);
+
   ArrayRef<Symbol *> getSymbols() const { return symVector; }
   Symbol *find(StringRef name);
 
diff --git a/lld/MachO/SymbolTable.cpp b/lld/MachO/SymbolTable.cpp
--- a/lld/MachO/SymbolTable.cpp
+++ b/lld/MachO/SymbolTable.cpp
@@ -56,6 +56,8 @@
 
   if (wasInserted)
     replaceSymbol<Undefined>(s, name);
+  else if (LazySymbol *lazy = dyn_cast<LazySymbol>(s))
+    lazy->fetchFile();
   return s;
 }
 
@@ -69,4 +71,17 @@
   return s;
 }
 
+Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
+                             const llvm::object::Archive::Symbol &sym) {
+  Symbol *s;
+  bool wasInserted;
+  std::tie(s, wasInserted) = insert(name);
+
+  if (wasInserted)
+    replaceSymbol<LazySymbol>(s, file, sym);
+  else if (isa<Undefined>(s))
+    file->fetch(sym);
+  return s;
+}
+
 SymbolTable *macho::symtab;
diff --git a/lld/MachO/Symbols.h b/lld/MachO/Symbols.h
--- a/lld/MachO/Symbols.h
+++ b/lld/MachO/Symbols.h
@@ -35,6 +35,7 @@
     DefinedKind,
     UndefinedKind,
     DylibKind,
+    LazyKind,
   };
 
   Kind kind() const { return static_cast<Kind>(symbolKind); }
@@ -79,6 +80,20 @@
   uint32_t gotIndex = UINT32_MAX;
 };
 
+class LazySymbol : public Symbol {
+public:
+  LazySymbol(ArchiveFile *file, const llvm::object::Archive::Symbol &sym)
+      : Symbol(LazyKind, sym.getName()), file(file), sym(sym) {}
+
+  static bool classof(const Symbol *s) { return s->kind() == LazyKind; }
+
+  InputFile *fetchFile();
+
+private:
+  ArchiveFile *file;
+  const llvm::object::Archive::Symbol sym;
+};
+
 inline uint64_t Symbol::getVA() const {
   if (auto *d = dyn_cast<Defined>(this))
     return d->isec->getVA() + d->value;
@@ -89,6 +104,7 @@
   alignas(Defined) char a[sizeof(Defined)];
   alignas(Undefined) char b[sizeof(Undefined)];
   alignas(DylibSymbol) char c[sizeof(DylibSymbol)];
+  alignas(LazySymbol) char d[sizeof(LazySymbol)];
 };
 
 template <typename T, typename... ArgT>
diff --git a/lld/MachO/Symbols.cpp b/lld/MachO/Symbols.cpp
--- a/lld/MachO/Symbols.cpp
+++ b/lld/MachO/Symbols.cpp
@@ -15,6 +15,8 @@
 using namespace lld;
 using namespace lld::macho;
 
+InputFile *LazySymbol::fetchFile() { return file->fetch(sym); }
+
 // Returns a symbol for an error message.
 std::string lld::toString(const Symbol &sym) {
   if (Optional<std::string> s = demangleItanium(sym.getName()))
diff --git a/lld/test/MachO/Inputs/archive2.s b/lld/test/MachO/Inputs/archive2.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/archive2.s
@@ -0,0 +1,4 @@
+.global _boo
+_boo:
+  mov $2, %rax
+  ret
diff --git a/lld/test/MachO/Inputs/archive3.s b/lld/test/MachO/Inputs/archive3.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/archive3.s
@@ -0,0 +1,4 @@
+.global _bar
+_bar:
+  mov $3, %rax
+  ret
diff --git a/lld/test/MachO/Inputs/archive4.s b/lld/test/MachO/Inputs/archive4.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/archive4.s
@@ -0,0 +1,4 @@
+.global _lonely
+_lonely:
+  mov $5, %rax
+  ret
diff --git a/lld/test/MachO/Inputs/f1.s b/lld/test/MachO/Inputs/f1.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/f1.s
@@ -0,0 +1,4 @@
+.global f
+f:
+  mov $1, %rax
+  ret
diff --git a/lld/test/MachO/Inputs/f2.s b/lld/test/MachO/Inputs/f2.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/f2.s
@@ -0,0 +1,4 @@
+.global f
+f:
+  mov $2, %rax
+  ret
diff --git a/lld/test/MachO/Inputs/f2g.s b/lld/test/MachO/Inputs/f2g.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/f2g.s
@@ -0,0 +1,9 @@
+.global f
+f:
+  mov $2, %rax
+  ret
+
+.global g
+g:
+  callq f
+  ret
diff --git a/lld/test/MachO/Inputs/g.s b/lld/test/MachO/Inputs/g.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/Inputs/g.s
@@ -0,0 +1,5 @@
+.global f
+.global g
+g:
+  callq f
+  ret
diff --git a/lld/test/MachO/archive.s b/lld/test/MachO/archive.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/archive.s
@@ -0,0 +1,26 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/archive2.s -o %t2.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/archive3.s -o %t3.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/archive4.s -o %t4.o
+
+# RUN: rm -f %t.a
+# RUN: llvm-ar rcs %t.a %t2.o %t3.o %t4.o
+# RUN: lld -flavor darwinnew %t.o %t.a -o %t.out
+
+## TODO: Run llvm-nm -p to validate symbol order
+# RUN: llvm-nm %t.out | FileCheck %s
+# CHECK: T _bar
+# CHECK: T _boo
+# CHECK: T _main
+
+# RUN: llvm-nm %t.out | FileCheck %s --check-prefix VISIBLE
+# VISIBLE-NOT: T _alone
+# VISIBLE-NOT: T _lonely
+
+.global _main
+_main:
+  callq _boo
+  callq _bar
+  mov $0, %rax
+  ret
diff --git a/lld/test/MachO/invalid/archive-no-index.s b/lld/test/MachO/invalid/archive-no-index.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/invalid/archive-no-index.s
@@ -0,0 +1,15 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/../Inputs/archive2.s -o %t2.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/../Inputs/archive3.s -o %t3.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/../Inputs/archive4.s -o %t4.o
+# RUN: rm -f %t.a
+# RUN: llvm-ar rcS %t.a %t2.o %t3.o %t4.o
+
+# RUN: not lld -flavor darwinnew %t.o %t.a -o /dev/null 2>&1 | FileCheck %s
+# CHECK: error: {{.*}}.a: archive has no index; run ranlib to add one
+
+.global _main
+_main:
+  mov $0, %rax
+  ret
diff --git a/lld/test/MachO/invalid/bad-archive.s b/lld/test/MachO/invalid/bad-archive.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/invalid/bad-archive.s
@@ -0,0 +1,11 @@
+# REQUIRES: x86
+# RUN: echo "!<arch>" > %t.a
+# RUN: echo "foo" >> %t.a
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
+
+# RUN: not lld -flavor darwinnew %t.o %t.a -o /dev/null 2>&1 | FileCheck -DFILE=%t.a %s
+# CHECK: error: [[FILE]]: failed to parse archive: truncated or malformed archive (remaining size of archive too small for next archive member header at offset 8)
+
+.global _main
+_main:
+  ret
diff --git a/lld/test/MachO/symbol-order.s b/lld/test/MachO/symbol-order.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/symbol-order.s
@@ -0,0 +1,32 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/g.s -o %tg.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/f1.s -o %tf1.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/f2.s -o %tf2.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %S/Inputs/f2g.s -o %tf2g.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
+
+# RUN: lld -flavor darwinnew -dylib -o %tlibf1.dylib %tf1.o
+
+# RUN: rm -f %tlibf2_g.a
+# RUN: llvm-ar rcs %tlibf2_g.a %tf2.o %tg.o
+
+# RUN: rm -f %tlibf2g.a
+# RUN: llvm-ar rcs %tlibf2g.a %tf2g.o
+
+# RUN: lld -flavor darwinnew %tlibf1.dylib %tlibf2_g.a %t.o -lSystem -o %t.out
+# RUN: ./%t.out; echo $? | FileCheck %s --check-prefix DYLIB-FIRST
+# DYLIB-FIRST: 1
+
+# RUN: lld -flavor darwinnew %tlibf2_g.a %tlibf1.dylib %t.o -lSystem -o %t.out
+# RUN: ./%t.out; echo $? | FileCheck %s --check-prefix ARCHIVE-FIRST
+# ARCHIVE-FIRST: 2
+
+# RUN: lld -flavor darwinnew %tlibf1.dylib %tlibf2g.a %t.o -lSystem -o %t.out
+# RUN: ./%t.out; echo $? | FileCheck %s --check-prefix ARCHIVE-PRIORITY
+# ARCHIVE-PRIORITY: 2
+
+.global g
+.global _main
+_main:
+  callq g
+  ret