diff --git a/lld/MachO/OutputSegment.h b/lld/MachO/OutputSegment.h
--- a/lld/MachO/OutputSegment.h
+++ b/lld/MachO/OutputSegment.h
@@ -10,7 +10,9 @@
 #define LLD_MACHO_OUTPUT_SEGMENT_H
 
 #include "OutputSection.h"
+#include "Symbols.h"
 #include "lld/Common/LLVM.h"
+#include "llvm/ADT/TinyPtrVector.h"
 
 #include <limits>
 #include <vector>
@@ -41,6 +43,7 @@
 public:
   void addOutputSection(OutputSection *os);
   void sortOutputSections();
+  void assignAddressesToStartEndSymbols();
 
   const std::vector<OutputSection *> &getSections() const { return sections; }
   size_t numNonHiddenSections() const;
@@ -55,6 +58,9 @@
   uint32_t initProt = 0;
   uint8_t index;
 
+  llvm::TinyPtrVector<Defined *> segmentStartSymbols;
+  llvm::TinyPtrVector<Defined *> segmentEndSymbols;
+
 private:
   std::vector<OutputSection *> sections;
 };
diff --git a/lld/MachO/OutputSegment.cpp b/lld/MachO/OutputSegment.cpp
--- a/lld/MachO/OutputSegment.cpp
+++ b/lld/MachO/OutputSegment.cpp
@@ -9,6 +9,7 @@
 #include "OutputSegment.h"
 #include "ConcatOutputSection.h"
 #include "InputSection.h"
+#include "Symbols.h"
 #include "SyntheticSections.h"
 
 #include "lld/Common/ErrorHandler.h"
@@ -145,6 +146,13 @@
   llvm::stable_sort(sections, compareByOrder<OutputSection *>(sectionOrder));
 }
 
+void OutputSegment::assignAddressesToStartEndSymbols() {
+  for (Defined *d : segmentStartSymbols)
+    d->value = addr;
+  for (Defined *d : segmentEndSymbols)
+    d->value = addr + vmSize;
+}
+
 void macho::sortOutputSegments() {
   llvm::stable_sort(outputSegments,
                     compareByOrder<OutputSegment *>(segmentOrder));
diff --git a/lld/MachO/SymbolTable.cpp b/lld/MachO/SymbolTable.cpp
--- a/lld/MachO/SymbolTable.cpp
+++ b/lld/MachO/SymbolTable.cpp
@@ -203,6 +203,12 @@
   End,
 };
 
+static Defined *createBoundarySymbol(const Undefined &sym) {
+  return symtab->addSynthetic(
+      sym.getName(), /*isec=*/nullptr, /*value=*/-1, /*isPrivateExtern=*/true,
+      /*includeInSymtab=*/false, /*referencedDynamically=*/false);
+}
+
 static void handleSectionBoundarySymbol(const Undefined &sym, StringRef segSect,
                                         Boundary which) {
   StringRef segName, sectName;
@@ -238,19 +244,19 @@
     inputSections.push_back(isec);
   }
 
-  Defined *boundarySym = symtab->addSynthetic(
-      sym.getName(), /*isec=*/nullptr, /*value=*/-1, /*isPrivateExtern=*/true,
-      /*includeInSymtab=*/false, /*referencedDynamically=*/false);
   if (which == Boundary::Start)
-    osec->sectionStartSymbols.push_back(boundarySym);
+    osec->sectionStartSymbols.push_back(createBoundarySymbol(sym));
   else
-    osec->sectionEndSymbols.push_back(boundarySym);
+    osec->sectionEndSymbols.push_back(createBoundarySymbol(sym));
 }
 
 static void handleSegmentBoundarySymbol(const Undefined &sym, StringRef segName,
                                         Boundary which) {
-  // FIXME
-  error("segment$start$ and segment$end$ symbols are not yet implemented");
+  OutputSegment *seg = getOrCreateOutputSegment(segName);
+  if (which == Boundary::Start)
+    seg->segmentStartSymbols.push_back(createBoundarySymbol(sym));
+  else
+    seg->segmentEndSymbols.push_back(createBoundarySymbol(sym));
 }
 
 void lld::macho::treatUndefinedSymbol(const Undefined &sym, StringRef source) {
diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -992,6 +992,7 @@
     addr = alignTo(addr, pageSize);
     seg->vmSize = addr - seg->addr;
     seg->fileSize = fileOff - seg->fileOff;
+    seg->assignAddressesToStartEndSymbols();
   }
 }
 
diff --git a/lld/test/MachO/start-end.s b/lld/test/MachO/start-end.s
--- a/lld/test/MachO/start-end.s
+++ b/lld/test/MachO/start-end.s
@@ -1,11 +1,10 @@
 # REQUIRES: x86
 
-## FIXME: Add tests for segment$start$foo, segment$end$foo once implemented.
-
 # RUN: rm -rf %t; split-file %s %t
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/main.s -o %t/main.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/seg.s -o %t/seg.o
 
 # RUN: %lld -lSystem %t/main.o %t/foo.o -o %t.out \
 # RUN:    -rename_section __FOO __bar __BAZ __quux \
@@ -171,6 +170,101 @@
 # CHECK: [[#%.16x, TEXTSTART]]
 # CHECK-NOT: [[#%.16x, TEXTEND]]
 
+###############################################################################
+## Test segment$start and segment$end.
+
+# RUN: %lld -lSystem %t/seg.o -o %t.seg.out \
+# RUN:    -rename_segment __FOO __BAZ \
+# RUN:    -rename_segment __WHAT __FOO \
+# RUN:    -u 'segment$start$__UFLAG_SEG' \
+# RUN:    -e 'segment$start$__TEXT'
+# RUN: llvm-objdump --macho --syms %t.seg.out > %t-seg-dump.txt
+## llvm-objdump can't dump segment names; use lld-otool for this.
+# RUN: llvm-otool -l %t.seg.out | grep -A6 LC_SEGMENT >> %t-seg-dump.txt
+# RUN: llvm-objdump --macho -d --no-symbolic-operands --no-show-raw-insn %t.seg.out >> %t-seg-dump.txt
+# RUN: llvm-objdump --macho --function-starts %t.out >> %t-seg-dump.txt
+# RUN: FileCheck %s --check-prefix=SEG < %t-seg-dump.txt
+
+# SEG-LABEL: SYMBOL TABLE:
+# SEG-NOT: segment$start$__TEXT
+# SEG-NOT: segment$end$__TEXT
+# SEG-NOT: segment$start$__FOO
+# SEG-NOT: segment$end$__FOO
+# SEG-NOT: segment$start$__BAZ
+# SEG-NOT: segment$end$__BAZ
+# SEG-NOT: segment$start$__WHAT
+# SEG-NOT: segment$end$__WHAT
+# SEG-NOT: segment$start$__UFLAG_SEG
+# SEG-NOT: segment$start$__UFLAG_SEG
+# SEG: segment$start$REGULAR
+# SEG: segment$end$REGULAR
+
+# SEG:           cmd LC_SEGMENT_64
+# SEG-NEXT:  cmdsize
+# SEG-NEXT:  segname __PAGEZERO
+
+# SEG:           cmd LC_SEGMENT_64
+# SEG-NEXT:  cmdsize
+# SEG-NEXT:  segname __TEXT
+# SEG-NEXT:   vmaddr 0x[[#%x, TEXTSTART:]]
+# SEG-NEXT:   vmsize 0x[[#%x, TEXTSIZE:]]
+
+# SEG:           cmd LC_SEGMENT_64
+# SEG-NEXT:  cmdsize
+# SEG-NEXT:  segname __BAZ
+# SEG-NEXT:   vmaddr 0x[[#%x, BAZSTART:]]
+# SEG-NEXT:   vmsize 0x[[#%x, BAZSIZE:]]
+
+# SEG:           cmd LC_SEGMENT_64
+# SEG-NEXT:  cmdsize
+# SEG-NEXT:  segname __FOO
+# SEG-NEXT:   vmaddr 0x[[#%x, FOOSTART:]]
+# SEG-NEXT:   vmsize 0x[[#%x, FOOSIZE:]]
+
+# SEG:           cmd LC_SEGMENT_64
+# SEG-NEXT:  cmdsize
+# SEG-NEXT:  segname __UFLAG_SEG
+# SEG-NEXT:   vmaddr 0x[[#%x, UFLAGSTART:]]
+# SEG-NEXT:   vmsize 0x0000000000000000
+
+# SEG:           cmd LC_SEGMENT_64
+# SEG-NEXT:  cmdsize
+# SEG-NEXT:  segname ASDF
+# SEG-NEXT:   vmaddr 0x[[#%x, ASDFSTART:]]
+# SEG-NEXT:   vmsize 0x0000000000000000
+
+# SEG: _main
+
+## segment$start$__TEXT / segment$end$__TEXT
+# SEG:      [[#%x, PC1:]]:
+# SEG-SAME: leaq [[#%d, TEXTSTART - PC1 - 7]](%rip), %rax
+# SEG-NEXT: [[#%x, PC2:]]:
+# SEG-SAME: leaq [[#%d, TEXTSTART + TEXTSIZE - PC2 - 7]](%rip), %rbx
+
+## segment$start$__FOO / segment$end$__FOO, which is renamed to __BAZ
+# SEG:      [[#%x, PC3:]]:
+# SEG-SAME: leaq [[#%d, BAZSTART - PC3 - 7]](%rip), %rax
+# SEG-NEXT: [[#%x, PC4:]]:
+# SEG-SAME: leaq [[#%d, BAZSTART + BAZSIZE - PC4 - 7]](%rip), %rbx
+
+## segment$start$__BAZ / segment$end$__BAZ
+# SEG:      [[#%x, PC5:]]:
+# SEG-SAME: leaq [[#%d, BAZSTART - PC5 - 7]](%rip), %rax
+# SEG-NEXT: [[#%x, PC6:]]:
+# SEG-SAME: leaq [[#%d, BAZSTART + BAZSIZE - PC6 - 7]](%rip), %rbx
+
+## segment$start$__WHAT / segment$end$__WHAT, which is renamed to __FOO
+# SEG:      [[#%x, PC7:]]:
+# SEG-SAME: leaq [[#%d, FOOSTART - PC7 - 7]](%rip), %rax
+# SEG-NEXT: [[#%x, PC8:]]:
+# SEG-SAME: leaq [[#%d, FOOSTART + FOOSIZE - PC8 - 7]](%rip), %rbx
+
+## segment$start$ASDF / segment$end$ASDF
+# SEG:      [[#%x, PC9:]]:
+# SEG-SAME: leaq [[#%d, ASDFSTART - PC9 - 7]](%rip), %rax
+# SEG-NEXT: [[#%x, PC10:]]:
+# SEG-SAME: leaq [[#%d, ASDFSTART - PC10 - 7]](%rip), %rbx
+
 #--- order.txt
 _otherfun
 _main
@@ -272,3 +366,53 @@
 .fill 1
 
 .subsections_via_symbols
+
+#--- seg.s
+## Renamed to __BAZ,__bar by -rename_segment
+.section __FOO,__bar
+.space 1
+
+## Renamed to __FOO,__ever by -rename_segment
+.section __WHAT,__ever
+.space 1
+
+.text
+.globl segment$start$REGULAR
+segment$start$REGULAR:
+  retq
+
+.globl segment$end$REGULAR
+segment$end$REGULAR:
+  retq
+
+.globl _main
+_main:
+  movq segment$start$__TEXT@GOTPCREL(%rip), %rax
+  movq segment$end$__TEXT@GOTPCREL(%rip), %rbx
+
+  movq segment$start$__FOO@GOTPCREL(%rip), %rax
+  movq segment$end$__FOO@GOTPCREL(%rip), %rbx
+
+  movq segment$start$__BAZ@GOTPCREL(%rip), %rax
+  movq segment$end$__BAZ@GOTPCREL(%rip), %rbx
+
+  # (These two lines make ld64 crash linking the .o file.
+  # The rest of the test works with ld64 too.)
+  movq segment$start$__WHAT@GOTPCREL(%rip), %rax
+  movq segment$end$__WHAT@GOTPCREL(%rip), %rbx
+
+  # References to non-existing segments create that segment,
+  # without any sections in it.
+  movq segment$start$ASDF@GOTPCREL(%rip), %rax
+  movq segment$end$ASDF@GOTPCREL(%rip), %rbx
+
+  ## Non-undefined symbols don't create segments.
+  callq segment$start$REGULAR
+  callq segment$end$REGULAR
+
+  ret
+
+.section __TEXT,__fill
+.space 578
+
+.subsections_via_symbols