diff --git a/clang-tools-extra/clangd/Hover.h b/clang-tools-extra/clangd/Hover.h
--- a/clang-tools-extra/clangd/Hover.h
+++ b/clang-tools-extra/clangd/Hover.h
@@ -58,7 +58,7 @@
   std::string Documentation;
   /// Source code containing the definition of the symbol.
   std::string Definition;
-
+  const char *DefinitionLanguage = "cpp";
   /// Access specifier for declarations inside class/struct/unions, empty for
   /// others.
   std::string AccessSpecifier;
diff --git a/clang-tools-extra/clangd/Hover.cpp b/clang-tools-extra/clangd/Hover.cpp
--- a/clang-tools-extra/clangd/Hover.cpp
+++ b/clang-tools-extra/clangd/Hover.cpp
@@ -920,6 +920,22 @@
   if (TokensTouchingCursor.empty())
     return llvm::None;
 
+  // Show full header file path if cursor is on include directive.
+  if (const auto MainFilePath =
+          getCanonicalPath(SM.getFileEntryForID(SM.getMainFileID()), SM)) {
+    for (const auto &Inc : AST.getIncludeStructure().MainFileIncludes) {
+      if (Inc.Resolved.empty() || Inc.HashLine != Pos.line)
+        continue;
+      HoverInfo HI;
+      HI.Name = std::string(llvm::sys::path::filename(Inc.Resolved));
+      // FIXME: We don't have a fitting value for Kind.
+      HI.Definition =
+          URIForFile::canonicalize(Inc.Resolved, *MainFilePath).file().str();
+      HI.DefinitionLanguage = "";
+      return HI;
+    }
+  }
+
   // To be used as a backup for highlighting the selected token, we use back as
   // it aligns better with biases elsewhere (editors tend to send the position
   // for the left of the hovered token).
@@ -998,6 +1014,7 @@
 
 markup::Document HoverInfo::present() const {
   markup::Document Output;
+
   // Header contains a text of the form:
   // variable `var`
   //
@@ -1098,7 +1115,8 @@
                                            : Definition;
     // Note that we don't print anything for global namespace, to not annoy
     // non-c++ projects or projects that are not making use of namespaces.
-    Output.addCodeBlock(ScopeComment + DefinitionWithAccess);
+    Output.addCodeBlock(ScopeComment + DefinitionWithAccess,
+                        DefinitionLanguage);
   }
 
   return Output;
diff --git a/clang-tools-extra/clangd/unittests/HoverTests.cpp b/clang-tools-extra/clangd/unittests/HoverTests.cpp
--- a/clang-tools-extra/clangd/unittests/HoverTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HoverTests.cpp
@@ -2760,6 +2760,15 @@
 
 // In test::Bar
 int foo = 3)",
+      },
+      {
+          [](HoverInfo &HI) {
+            HI.Name = "stdio.h";
+            HI.Definition = "/usr/include/stdio.h";
+          },
+          R"(stdio.h
+
+/usr/include/stdio.h)",
       }};
 
   for (const auto &C : Cases) {