Index: ELF/Relocations.cpp
===================================================================
--- ELF/Relocations.cpp
+++ ELF/Relocations.cpp
@@ -691,8 +691,65 @@
 
 static std::vector<UndefinedDiag> undefs;
 
+static const Symbol *correctSpelling(const Symbol &sym) {
+  // Build a map of local defined symbols.
+  DenseMap<StringRef, const Symbol *> map;
+  if (sym.file)
+    for (const Symbol *s : sym.file->getSymbols())
+      if (s->isLocal() && s->isDefined())
+        map.try_emplace(s->getName(), s);
+
+  const Symbol *corrected = nullptr;
+  auto suggest = [&](StringRef newName) {
+    // Test if the name is defined locally.
+    const Symbol *s = map.lookup(newName);
+    if (s) {
+      corrected = s;
+      return true;
+    }
+
+    // Test if the name is in the symbol table and is not undefined.
+    s = symtab->find(newName);
+    if (s && !s->isUndefined()) {
+      corrected = s;
+      return true;
+    }
+    return false;
+  };
+
+  StringRef name = sym.getName();
+  for (size_t i = 0, e = name.size(); i != e + 1; ++i) {
+    // Insert a character before name[i].
+    std::string newName = (name.substr(0, i) + "0" + name.substr(i)).str();
+    for (char c = '0'; c <= 'z'; ++c) {
+      newName[i] = c;
+      if (suggest(newName))
+        break;
+    }
+    if (corrected || i == e)
+      break;
+
+    // Substitute name[i].
+    newName = name;
+    for (char c = '0'; c <= 'z'; ++c) {
+      newName[i] = c;
+      if (suggest(newName))
+        break;
+    }
+    if (corrected)
+      break;
+
+    // Delete name[i].
+    if (suggest((name.substr(0, i) + name.substr(i + 1)).str()))
+      break;
+  }
+
+  return corrected;
+}
+
 template <class ELFT>
-static void reportUndefinedSymbol(const UndefinedDiag &undef) {
+static void reportUndefinedSymbol(const UndefinedDiag &undef,
+                                  bool spellCorrector) {
   Symbol &sym = *undef.sym;
 
   auto visibility = [&]() -> std::string {
@@ -732,6 +789,13 @@
     msg += ("\n>>> referenced " + Twine(undef.locs.size() - i) + " more times")
                .str();
 
+  if (spellCorrector)
+    if (const Symbol *corrected = correctSpelling(sym)) {
+      msg += "\n>>> did you mean: " + toString(*corrected);
+      if (corrected->file)
+        msg += "\n>>> defined in: " + toString(corrected->file);
+    }
+
   if (sym.getName().startswith("_ZTV"))
     msg += "\nthe vtable symbol may be undefined because the class is missing "
            "its key function (see https://lld.llvm.org/missingkeyfunction)";
@@ -755,10 +819,13 @@
       firstRef[undef.sym] = &undef;
   }
 
-  for (const UndefinedDiag &undef : undefs) {
-    if (!undef.locs.empty())
-      reportUndefinedSymbol<ELFT>(undef);
-  }
+  size_t i = 0;
+  for (const UndefinedDiag &undef : undefs)
+    if (!undef.locs.empty()) {
+      // Enable spell corrector for the first 2 diagnostics.
+      reportUndefinedSymbol<ELFT>(undef, i < 2);
+      ++i;
+    }
   undefs.clear();
 }
 
Index: test/ELF/undef-spell-corrector.s
===================================================================
--- /dev/null
+++ test/ELF/undef-spell-corrector.s
@@ -0,0 +1,61 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+
+## Insert a character.
+## The spell corrector is enabled for the first two "undefined symbol" diagnostics.
+# RUN: echo 'call bcde; call abcd; call abde' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: not ld.lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=INSERT %s -DFILE=%t.o
+
+## Symbols defined in DSO can be suggested.
+# RUN: ld.lld %t.o -shared -o %t.so
+# RUN: not ld.lld %t.so %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=INSERT %s -DFILE=%t.so
+
+# INSERT:      error: undefined symbol: bcde
+# INSERT-NEXT: >>> referenced by {{.*}}
+# INSERT-NEXT: >>> did you mean: abcde
+# INSERT-NEXT: >>> defined in: [[FILE]]
+# INSERT:      error: undefined symbol: abcd
+# INSERT-NEXT: >>> referenced by {{.*}}
+# INSERT-NEXT: >>> did you mean: abcde
+# INSERT-NEXT: >>> defined in: [[FILE]]
+# INSERT:      error: undefined symbol: abde
+# INSERT-NEXT: >>> referenced by {{.*}}
+# INSERT-NOT:  >>>
+
+## Substitute a character.
+# RUN: echo 'call bbcde; call abcdd' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: not ld.lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=SUBST %s
+
+# SUBST:      error: undefined symbol: bbcde
+# SUBST-NEXT: >>> referenced by {{.*}}
+# SUBST-NEXT: >>> did you mean: abcde
+# SUBST:      error: undefined symbol: abcdd
+# SUBST-NEXT: >>> referenced by {{.*}}
+# SUBST-NEXT: >>> did you mean: abcde
+
+## Delete a character.
+# RUN: echo 'call aabcde; call abcdee' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: not ld.lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=DELETE %s
+
+# DELETE:      error: undefined symbol: aabcde
+# DELETE-NEXT: >>> referenced by {{.*}}
+# DELETE-NEXT: >>> did you mean: abcde
+# DELETE:      error: undefined symbol: abcdee
+# DELETE-NEXT: >>> referenced by {{.*}}
+# DELETE-NEXT: >>> did you mean: abcde
+
+## Missing const qualifier
+# RUN: echo 'call _Z3fooPi' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: not ld.lld %t.o %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=CONST %s
+## Local defined symbols
+# RUN: echo '_Z3fooPKi: call _Z3fooPi' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: not ld.lld %t1.o -o /dev/null 2>&1 | FileCheck --check-prefix=CONST %s
+
+# CONST:      error: undefined symbol: foo(int*)
+# CONST-NEXT: >>> referenced by {{.*}}
+# CONST-NEXT: >>> did you mean: foo(int const*)
+
+.globl _start, abcde, _Z3fooPKi
+_start:
+abcde:
+_Z3fooPKi: