diff --git a/verilog/formatting/formatter_test.cc b/verilog/formatting/formatter_test.cc
index e313bdc85..c0c26bc7c 100644
--- a/verilog/formatting/formatter_test.cc
+++ b/verilog/formatting/formatter_test.cc
@@ -157,6 +157,14 @@ static const std::initializer_list<FormatterTestCase> kFormatterTestCases = {
      "`ifndef FOO\n"
      "`define BAR\n\n"
      "`endif\n"},
+    {"`define    FOO   \\\n"
+     "  BAR\n",
+     "`define FOO \\\n"  // TODO(b/72527558): right align '\'s to column limit
+     "  BAR\n"},
+    {"`define    FOOOOOOOOOOOOOOOO   \\\n"
+     "  BAAAAAAAAAAAAAAAAR BAAAAAAAAAAAAAZ;\n",
+     "`define FOOOOOOOOOOOOOOOO \\\n"  // macro text starts at '\'
+     "  BAAAAAAAAAAAAAAAAR BAAAAAAAAAAAAAZ;\n"},
     {"`ifdef      FOO\n"
      "  `fine()\n"
      "`else\n"
diff --git a/verilog/formatting/token_annotator.cc b/verilog/formatting/token_annotator.cc
index 201dccd59..5c4319852 100644
--- a/verilog/formatting/token_annotator.cc
+++ b/verilog/formatting/token_annotator.cc
@@ -590,6 +590,18 @@ static WithReason<SpacingOptions> BreakDecisionBetween(
     }
   }
 
+  if (left.TokenEnum() == PP_define) {
+    return {SpacingOptions::MustAppend,
+            "Keep `define and macro name together."};
+  }
+  if (right.TokenEnum() == PP_define_body) {
+    // TODO(b/141517267): reflow macro definition text with flexible
+    // line-continuations.
+    return {SpacingOptions::MustAppend,
+            "Macro definition body must start on same line (but may be "
+            "line-continued)."};
+  }
+
   // Check for mandatory line breaks.
   if (left.format_token_enum == FTT::eol_comment ||
       left.TokenEnum() == PP_define_body  // definition excludes trailing '\n'
diff --git a/verilog/formatting/token_annotator_test.cc b/verilog/formatting/token_annotator_test.cc
index 7fd8efdcd..5b0716046 100644
--- a/verilog/formatting/token_annotator_test.cc
+++ b/verilog/formatting/token_annotator_test.cc
@@ -782,7 +782,7 @@ TEST(TokenAnnotatorTest, AnnotateFormattingInfoTest) {
           {DefaultStyle,
            0,
            {{0, SpacingOptions::Undecided},   //  `define
-            {1, SpacingOptions::Undecided},   //  FOO
+            {1, SpacingOptions::MustAppend},  //  FOO
             {0, SpacingOptions::Undecided},   //  (
             {0, SpacingOptions::Undecided},   //  name
             {1, SpacingOptions::Undecided},   //  =
@@ -1086,12 +1086,12 @@ TEST(TokenAnnotatorTest, AnnotateFormattingInfoTest) {
           {DefaultStyle,
            1,
            {
-               {0, SpacingOptions::Undecided},  // `define
-               {1, SpacingOptions::Undecided},  // FOO
-               {0, SpacingOptions::Undecided},  // "" (empty definition body)
-               {0, SpacingOptions::MustWrap},   // `define
-               {1, SpacingOptions::Undecided},  // BAR
-               {0, SpacingOptions::Undecided},  // "" (empty definition body)
+               {0, SpacingOptions::Undecided},   // `define
+               {1, SpacingOptions::MustAppend},  // FOO
+               {0, SpacingOptions::MustAppend},  // "" (empty definition body)
+               {0, SpacingOptions::MustWrap},    // `define
+               {1, SpacingOptions::MustAppend},  // BAR
+               {0, SpacingOptions::MustAppend},  // "" (empty definition body)
            },
            {
                {yytokentype::PP_define, "`define"},
@@ -1107,12 +1107,12 @@ TEST(TokenAnnotatorTest, AnnotateFormattingInfoTest) {
           {DefaultStyle,
            1,
            {
-               {0, SpacingOptions::Undecided},  // `define
-               {1, SpacingOptions::Undecided},  // FOO
-               {1, SpacingOptions::Undecided},  // 1
-               {1, SpacingOptions::MustWrap},   // `define
-               {1, SpacingOptions::Undecided},  // BAR
-               {1, SpacingOptions::Undecided},  // 2
+               {0, SpacingOptions::Undecided},   // `define
+               {1, SpacingOptions::MustAppend},  // FOO
+               {1, SpacingOptions::MustAppend},  // 1
+               {1, SpacingOptions::MustWrap},    // `define
+               {1, SpacingOptions::MustAppend},  // BAR
+               {1, SpacingOptions::MustAppend},  // 2
            },
            {
                {yytokentype::PP_define, "`define"},
@@ -1130,26 +1130,26 @@ TEST(TokenAnnotatorTest, AnnotateFormattingInfoTest) {
            1,
            {
                {0, SpacingOptions::Undecided},   // `define
-               {1, SpacingOptions::Undecided},   // FOO
+               {1, SpacingOptions::MustAppend},  // FOO
                {0, SpacingOptions::MustAppend},  // (
                {0, SpacingOptions::Undecided},   // )
-               {0, SpacingOptions::Undecided},   // "" (empty definition body)
+               {0, SpacingOptions::MustAppend},  // "" (empty definition body)
 
                {0, SpacingOptions::MustWrap},    // `define
-               {1, SpacingOptions::Undecided},   // BAR
+               {1, SpacingOptions::MustAppend},  // BAR
                {0, SpacingOptions::MustAppend},  // (
                {0, SpacingOptions::Undecided},   // x
                {0, SpacingOptions::Undecided},   // )
-               {0, SpacingOptions::Undecided},   // "" (empty definition body)
+               {0, SpacingOptions::MustAppend},  // "" (empty definition body)
 
                {0, SpacingOptions::MustWrap},    // `define
-               {1, SpacingOptions::Undecided},   // BAZ
+               {1, SpacingOptions::MustAppend},  // BAZ
                {0, SpacingOptions::MustAppend},  // (
                {0, SpacingOptions::Undecided},   // y
                {0, SpacingOptions::Undecided},   // ,
                {1, SpacingOptions::Undecided},   // z
                {0, SpacingOptions::Undecided},   // )
-               {0, SpacingOptions::Undecided},   // "" (empty definition body)
+               {0, SpacingOptions::MustAppend},  // "" (empty definition body)
            },
            {
                {yytokentype::PP_define, "`define"},
@@ -1181,13 +1181,13 @@ TEST(TokenAnnotatorTest, AnnotateFormattingInfoTest) {
               1,
               {
                   {0, SpacingOptions::Undecided},   // `define
-                  {1, SpacingOptions::Undecided},   // ADD
+                  {1, SpacingOptions::MustAppend},  // ADD
                   {0, SpacingOptions::MustAppend},  // (
                   {0, SpacingOptions::Undecided},   // y
                   {0, SpacingOptions::Undecided},   // ,
                   {1, SpacingOptions::Undecided},   // z
                   {0, SpacingOptions::Undecided},   // )
-                  {1, SpacingOptions::Undecided},   // "y+z"
+                  {1, SpacingOptions::MustAppend},  // "y+z"
               },
               {
                   {yytokentype::PP_define, "`define"},
@@ -1977,6 +1977,13 @@ TEST(TokenAnnotatorTest, AnnotateFormattingWithContextTest) {
           {},  // any context
           {1, SpacingOptions::MustWrap},
       },
+      {
+          DefaultStyle,
+          {yytokentype::PP_define, "`define"},
+          {SymbolIdentifier, "ID"},
+          {},  // any context
+          {1, SpacingOptions::MustAppend},
+      },
       {
           DefaultStyle,
           {TK_StringLiteral, "\"lost/file.svh\""},