diff --git a/lld/ELF/Arch/AVR.cpp b/lld/ELF/Arch/AVR.cpp
--- a/lld/ELF/Arch/AVR.cpp
+++ b/lld/ELF/Arch/AVR.cpp
@@ -26,6 +26,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "InputFiles.h"
+#include "OutputSections.h"
 #include "Symbols.h"
 #include "Target.h"
 #include "lld/Common/ErrorHandler.h"
@@ -47,6 +48,9 @@
                      const uint8_t *loc) const override;
   void relocate(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
+  void relocateAlloc(InputSectionBase &sec, uint8_t *buf) const override;
+  bool tryRelaxLongJumpCall(uint8_t *loc, uint64_t callAddr,
+                            uint64_t destAddr) const;
 };
 } // namespace
 
@@ -234,6 +238,57 @@
   return cast<ObjFile<ELF32LE>>(file)->getObj().getHeader().e_flags;
 }
 
+// Try to relax
+//     jmp _foo   ; 4-byte instruction
+// to
+//     rjmp _foo  ; 2-byte instruction
+//     nop        ; 2-byte instruction
+bool AVR::tryRelaxLongJumpCall(uint8_t *loc, uint64_t callAddr,
+                               uint64_t destAddr) const {
+  // The offset must be in range [-4094, 4096].
+  const int64_t Off = destAddr - callAddr;
+  if (Off < -4094 || Off > 4096)
+    return false;
+
+  // Set the first instruction to RCALL/RJMP.
+  const uint16_t OffCode = static_cast<uint64_t>(Off - 2) >> 1;
+  const uint16_t OpCode = read16le(loc) == 0x940c ? 0xc000 : 0xd000;
+  write16le(loc, OpCode | (OffCode & 0xfff));
+
+  // Set the second instruction to NOP.
+  write16le(loc + 2, 0);
+
+  return true;
+}
+
+void AVR::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const {
+  uint64_t secAddr = sec.getOutputSection()->addr;
+  if (auto *s = dyn_cast<InputSection>(&sec))
+    secAddr += s->outSecOff;
+  for (const Relocation &rel : sec.relocs()) {
+    uint8_t *loc = buf + rel.offset;
+    const uint64_t val = SignExtend64(
+        sec.getRelocTargetVA(sec.file, rel.type, rel.addend,
+                             secAddr + rel.offset, *rel.sym, rel.expr),
+        32);
+
+    switch (rel.type) {
+    // Try to relax a long jump/call (a 4-byte instruction) to a pair of
+    // short jump/call (a 2-byte instruction) and nop (a 2-byte instruction).
+    case R_AVR_CALL:
+      if (config->relax &&
+          (getEFlags(ctx.objectFiles[0]) & EF_AVR_LINKRELAX_PREPARED) != 0)
+        if (tryRelaxLongJumpCall(loc, secAddr + rel.offset, val))
+          continue;
+      [[fallthrough]];
+
+    default:
+      relocate(loc, rel, val);
+      break;
+    }
+  }
+}
+
 uint32_t AVR::calcEFlags() const {
   assert(!ctx.objectFiles.empty());
 
diff --git a/lld/test/ELF/avr-relax.s b/lld/test/ELF/avr-relax.s
new file mode 100644
--- /dev/null
+++ b/lld/test/ELF/avr-relax.s
@@ -0,0 +1,39 @@
+# REQUIRES: avr
+# RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328p %s -o %t.o
+# RUN: ld.lld %t.o -o %t0.exe -Ttext=0 --no-relax
+# RUN: llvm-objdump -d %t0.exe --mcpu=atmega328 | FileCheck %s --check-prefix=NORELAX
+# RUN: ld.lld %t.o -o %t1.exe -Ttext=0
+# RUN: llvm-objdump -d %t1.exe --mcpu=atmega328 | FileCheck %s --check-prefix=RELAX
+
+main:
+  call foo
+  rcall foo
+foo:
+  jmp foo
+  rjmp foo
+
+la0:
+  jmp la1
+  .zero 4096
+la1:
+  jmp la0
+
+# NORELAX:      <main>:
+# NORELAX-NEXT:   0: 0e 94 03 00   call  0x6
+# NORELAX-NEXT:   4: 00 d0         rcall .+0
+# NORELAX:      <foo>:
+# NORELAX-NEXT:   6: 0c 94 03 00   jmp   0x6
+# NORELAX-NEXT:   a: fd cf         rjmp  .-6
+
+# RELAX:        <main>:
+# RELAX-NEXT:     0: 02 d0         rcall .+4
+# RELAX-NEXT:     2: 00 00         nop
+# RELAX-NEXT:     4: 00 d0         rcall .+0
+# RELAX:        <foo>:
+# RELAX-NEXT:     6: ff cf         rjmp  .-2
+# RELAX-NEXT:     8: 00 00         nop
+# RELAX-NEXT:     a: fd cf         rjmp  .-6
+# RELAX:        <la0>:
+# RELAX-NEXT:     c: 0c 94 08 08   jmp   0x1010
+# RELAX:        <la1>:
+# RELAX-NEXT:  1010: 0c 94 06 00   jmp   0xc
diff --git a/lld/test/ELF/basic-avr.s b/lld/test/ELF/basic-avr.s
--- a/lld/test/ELF/basic-avr.s
+++ b/lld/test/ELF/basic-avr.s
@@ -1,7 +1,6 @@
-# REQUIRES: avr
-# RUN: llvm-mc -filetype=obj -triple=avr-unknown-linux -mcpu=atmega328p %s -o %t.o
-# RUN: ld.lld %t.o -o %t.exe -Ttext=0
-# RUN: llvm-objdump -d %t.exe | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328p %s -o %t.o
+# RUN: ld.lld %t.o -o %t.exe -Ttext=0 --no-relax
+# RUN: llvm-objdump -d %t.exe --mcpu=atmega328 | FileCheck %s
 
 main:
   call foo
@@ -9,6 +8,6 @@
   jmp foo
 
 # CHECK:      <main>:
-# CHECK-NEXT:   0: 0e 94 02 00 <unknown>
+# CHECK-NEXT:   0: 0e 94 02 00   call  0x4
 # CHECK:      <foo>:
-# CHECK-NEXT:   4: 0c 94 02 00 <unknown>
+# CHECK-NEXT:   4: 0c 94 02 00   jmp   0x4