diff --git a/mlir/tools/mlir-opt/mlir-opt.cpp b/mlir/tools/mlir-opt/mlir-opt.cpp
--- a/mlir/tools/mlir-opt/mlir-opt.cpp
+++ b/mlir/tools/mlir-opt/mlir-opt.cpp
@@ -11,6 +11,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Analysis/Passes.h"
+#include "mlir/IR/Dialect.h"
+#include "mlir/IR/MLIRContext.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Pass/PassManager.h"
 #include "mlir/Support/FileUtilities.h"
@@ -47,6 +49,11 @@
                  cl::desc("Run the verifier after each transformation pass"),
                  cl::init(true));
 
+static cl::opt<bool>
+    showDialects("show-dialects",
+                 cl::desc("Print the list of registered dialects"),
+                 cl::init(false));
+
 int main(int argc, char **argv) {
   InitLLVM y(argc, argv);
 
@@ -57,6 +64,15 @@
   // Parse pass names in main to ensure static initialization completed.
   cl::ParseCommandLineOptions(argc, argv, "MLIR modular optimizer driver\n");
 
+  MLIRContext context;
+  if(showDialects) {
+    llvm::outs() << "Registered Dialects:\n";
+    for(Dialect *dialect : context.getRegisteredDialects()) {
+      llvm::outs() << dialect->getNamespace() << "\n";
+    }
+    return 0;
+  }
+
   // Set up the input file.
   std::string errorMessage;
   auto file = openInputFile(inputFilename, &errorMessage);