diff --git a/clang-tools-extra/clangd/index/remote/server/Server.cpp b/clang-tools-extra/clangd/index/remote/server/Server.cpp
--- a/clang-tools-extra/clangd/index/remote/server/Server.cpp
+++ b/clang-tools-extra/clangd/index/remote/server/Server.cpp
@@ -37,7 +37,9 @@
 #include <grpc++/grpc++.h>
 #include <grpc++/health_check_service_interface.h>
 #include <memory>
+#include <string>
 #include <thread>
+#include <utility>
 
 #if ENABLE_GRPC_REFLECTION
 #include <grpc++/ext/proto_server_reflection_plugin.h>
@@ -78,6 +80,12 @@
     llvm::cl::init(false),
 };
 
+llvm::cl::opt<std::string> LogPrefix{
+    "log-prefix",
+    llvm::cl::desc("A string that'll be prepended to all log statements. "
+                   "Useful when running multiple instances on same host."),
+};
+
 llvm::cl::opt<std::string> TraceFile(
     "trace-file",
     llvm::cl::desc("Path to the file where tracer logs will be stored"));
@@ -427,27 +435,48 @@
   ServerShutdownWatcher.join();
 }
 
-std::unique_ptr<Logger> makeLogger(llvm::raw_ostream &OS) {
-  if (!LogPublic)
-    return std::make_unique<StreamLogger>(OS, LogLevel);
-  // Redacted mode:
-  //  - messages outside the scope of a request: log fully
-  //  - messages tagged [public]: log fully
-  //  - errors: log the format string
-  //  - others: drop
-  class RedactedLogger : public StreamLogger {
+std::unique_ptr<Logger> makeLogger(llvm::StringRef LogPrefix,
+                                   llvm::raw_ostream &OS) {
+  std::unique_ptr<Logger> Base;
+  if (LogPublic) {
+    // Redacted mode:
+    //  - messages outside the scope of a request: log fully
+    //  - messages tagged [public]: log fully
+    //  - errors: log the format string
+    //  - others: drop
+    class RedactedLogger : public StreamLogger {
+    public:
+      using StreamLogger::StreamLogger;
+      void log(Level L, const char *Fmt,
+               const llvm::formatv_object_base &Message) override {
+        if (Context::current().get(CurrentRequest) == nullptr ||
+            llvm::StringRef(Fmt).startswith("[public]"))
+          return StreamLogger::log(L, Fmt, Message);
+        if (L >= Error)
+          return StreamLogger::log(L, Fmt,
+                                   llvm::formatv("[redacted] {0}", Fmt));
+      }
+    };
+    Base = std::make_unique<RedactedLogger>(OS, LogLevel);
+  } else {
+    Base = std::make_unique<StreamLogger>(OS, LogLevel);
+  }
+
+  if (LogPrefix.empty())
+    return Base;
+  class PrefixedLogger : public Logger {
+    std::string LogPrefix;
+    std::unique_ptr<Logger> Base;
+
   public:
-    using StreamLogger::StreamLogger;
+    PrefixedLogger(llvm::StringRef LogPrefix, std::unique_ptr<Logger> Base)
+        : LogPrefix(LogPrefix.str()), Base(std::move(Base)) {}
     void log(Level L, const char *Fmt,
              const llvm::formatv_object_base &Message) override {
-      if (Context::current().get(CurrentRequest) == nullptr ||
-          llvm::StringRef(Fmt).startswith("[public]"))
-        return StreamLogger::log(L, Fmt, Message);
-      if (L >= Error)
-        return StreamLogger::log(L, Fmt, llvm::formatv("[redacted] {0}", Fmt));
+      Base->log(L, Fmt, llvm::formatv("[{0}] {1}", LogPrefix, Message));
     }
   };
-  return std::make_unique<RedactedLogger>(OS, LogLevel);
+  return std::make_unique<PrefixedLogger>(LogPrefix, std::move(Base));
 }
 
 } // namespace
@@ -471,7 +500,7 @@
   llvm::errs().SetBuffered();
   // Don't flush stdout when logging for thread safety.
   llvm::errs().tie(nullptr);
-  auto Logger = makeLogger(llvm::errs());
+  auto Logger = makeLogger(LogPrefix.getValue(), llvm::errs());
   clang::clangd::LoggingSession LoggingSession(*Logger);
 
   llvm::Optional<llvm::raw_fd_ostream> TracerStream;
diff --git a/clang-tools-extra/clangd/test/remote-index/log-prefix.test b/clang-tools-extra/clangd/test/remote-index/log-prefix.test
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/clangd/test/remote-index/log-prefix.test
@@ -0,0 +1,18 @@
+# RUN: rm -rf %t
+# RUN: clangd-indexer %S/Inputs/Source.cpp > %t.idx
+# RUN: %python %S/pipeline_helper.py --input-file-name=%s --server-arg=--log=verbose --server-arg=-log-prefix=test-prefix --server-log=%t.log --project-root=%S --index-file=%t.idx > /dev/null
+# RUN: FileCheck %s < %t.log
+# REQUIRES: clangd-remote-index
+
+# CHECK: [test-prefix] Server listening on
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
+---
+{"jsonrpc":"2.0","id":1,"method":"workspace/symbol","params":{"query":"gFoo"}}
+# CHECK: [test-prefix] <<< FuzzyFindRequest
+# CHECK: [test-prefix] >>> FuzzyFindReply
+# CHECK: [test-prefix] [public] request v1/FuzzyFind
+---
+{"jsonrpc":"2.0","id":4,"method":"shutdown"}
+---
+{"jsonrpc":"2.0","method":"exit"}
+