diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -532,6 +532,20 @@
   }
 };
 
+/// Lower `fir.boxproc_host` operation. Extracts the host pointer from the
+/// boxproc.
+/// TODO: Part of supporting Fortran 2003 procedure pointers.
+struct BoxProcHostOpConversion : public FIROpConversion<fir::BoxProcHostOp> {
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::BoxProcHostOp boxprochost, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    return rewriter.notifyMatchFailure(
+        boxprochost, "fir.boxproc_host codegen is not implemented yet");
+  }
+};
+
 /// Lower `fir.box_tdesc` to the sequence of operations to extract the type
 /// descriptor from the box.
 struct BoxTypeDescOpConversion : public FIROpConversion<fir::BoxTypeDescOp> {
@@ -1529,6 +1543,20 @@
   }
 };
 
+/// Lower `fir.emboxproc` operation. Creates a procedure box.
+/// TODO: Part of supporting Fortran 2003 procedure pointers.
+struct EmboxProcOpConversion : public FIROpConversion<fir::EmboxProcOp> {
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::EmboxProcOp emboxproc, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    return rewriter.notifyMatchFailure(
+        emboxproc, "fir.emboxproc codegen is not implemented yet");
+  }
+};
+
+
 // Code shared between insert_value and extract_value Ops.
 struct ValueOpCommon {
   // Translate the arguments pertaining to any multidimensional array to
@@ -2035,6 +2063,20 @@
   }
 };
 
+/// Lower `fir.unboxproc` operation. Unbox a procedure box value, yielding its
+/// components.
+/// TODO: Part of supporting Fortran 2003 procedure pointers.
+struct UnboxProcOpConversion : public FIROpConversion<fir::UnboxProcOp> {
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::UnboxProcOp unboxproc, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    return rewriter.notifyMatchFailure(
+        unboxproc, "fir.unboxproc codegen is not implemented yet");
+  }
+};
+
 } // namespace
 
 namespace {
@@ -2061,20 +2103,21 @@
         AbsentOpConversion, AddcOpConversion, AddrOfOpConversion,
         AllocaOpConversion, BoxAddrOpConversion, BoxCharLenOpConversion,
         BoxDimsOpConversion, BoxEleSizeOpConversion, BoxIsAllocOpConversion,
-        BoxIsArrayOpConversion, BoxIsPtrOpConversion, BoxRankOpConversion,
-        BoxTypeDescOpConversion, CallOpConversion, CmpcOpConversion,
-        ConstcOpConversion, ConvertOpConversion, DispatchOpConversion,
-        DispatchTableOpConversion, DTEntryOpConversion, DivcOpConversion,
-        EmboxOpConversion, EmboxCharOpConversion, ExtractValueOpConversion,
-        HasValueOpConversion, GenTypeDescOpConversion, GlobalLenOpConversion,
-        GlobalOpConversion, InsertOnRangeOpConversion, InsertValueOpConversion,
+        BoxIsArrayOpConversion, BoxIsPtrOpConversion, BoxProcHostOpConversion,
+        BoxRankOpConversion, BoxTypeDescOpConversion, CallOpConversion,
+        CmpcOpConversion, ConstcOpConversion, ConvertOpConversion,
+        DispatchOpConversion, DispatchTableOpConversion, DTEntryOpConversion,
+        DivcOpConversion, EmboxOpConversion, EmboxCharOpConversion,
+        EmboxProcOpConversion, ExtractValueOpConversion, HasValueOpConversion,
+        GenTypeDescOpConversion, GlobalLenOpConversion, GlobalOpConversion,
+        InsertOnRangeOpConversion, InsertValueOpConversion,
         IsPresentOpConversion, LoadOpConversion, NegcOpConversion,
         MulcOpConversion, SelectCaseOpConversion, SelectOpConversion,
         SelectRankOpConversion, SelectTypeOpConversion, ShapeOpConversion,
         ShapeShiftOpConversion, ShiftOpConversion, SliceOpConversion,
         StoreOpConversion, StringLitOpConversion, SubcOpConversion,
-        UnboxCharOpConversion, UndefOpConversion, UnreachableOpConversion,
-        ZeroOpConversion>(typeConverter);
+        UnboxCharOpConversion, UnboxProcOpConversion, UndefOpConversion,
+        UnreachableOpConversion, ZeroOpConversion>(typeConverter);
     mlir::populateStdToLLVMConversionPatterns(typeConverter, pattern);
     mlir::arith::populateArithmeticToLLVMConversionPatterns(typeConverter,
                                                             pattern);
diff --git a/flang/lib/Optimizer/CodeGen/TypeConverter.h b/flang/lib/Optimizer/CodeGen/TypeConverter.h
--- a/flang/lib/Optimizer/CodeGen/TypeConverter.h
+++ b/flang/lib/Optimizer/CodeGen/TypeConverter.h
@@ -54,6 +54,11 @@
       LLVM_DEBUG(llvm::dbgs() << "type convert: " << boxchar << '\n');
       return convertType(specifics->boxcharMemoryType(boxchar.getEleTy()));
     });
+    addConversion([&](BoxProcType boxproc) {
+      // TODO: Support for this type will be added later when the Fortran 2003
+      // procedure pointer feature is implemented.
+      return llvm::None;
+    });
     addConversion(
         [&](fir::CharacterType charTy) { return convertCharType(charTy); });
     addConversion([&](HeapType heap) { return convertPointerLike(heap); });
diff --git a/flang/test/Fir/convert-to-llvm-invalid.fir b/flang/test/Fir/convert-to-llvm-invalid.fir
--- a/flang/test/Fir/convert-to-llvm-invalid.fir
+++ b/flang/test/Fir/convert-to-llvm-invalid.fir
@@ -148,3 +148,28 @@
   %1 = fir.array_coor %arg0(%0) %i, %j : (!fir.ref<!fir.array<?x?xf32>>, !fir.shapeshift<2>, index, index) -> !fir.ref<f32>
   return
 }
+
+// -----
+
+// Test that the type `fir.boxproc` fails to be legalized.
+// Not implemented yet.
+
+// expected-error@+1{{failed to legalize operation 'builtin.func'}}
+func private @foo0(%arg0: !fir.boxproc<() -> ()>)
+
+// -----
+
+// Test that `fir.emboxproc` fails to be legalized.
+// Not implemented yet.
+
+func private @method_impl(i32)
+
+func @emboxproc_test() {
+  %host_vars = fir.alloca tuple<i32,f64>
+// expected-error@+1{{failed to legalize operation 'fir.emboxproc'}}
+  %bproc = fir.emboxproc @method_impl, %host_vars : ((i32) -> (), !fir.ref<tuple<i32,f64>>) -> !fir.boxproc<(i32) -> ()>
+  return
+}
+
+// Test that `fir.unboxproc` and `fir.boxproc_host` also fails to be legalized.
+// At the moment these cannot be tested since the `fir.boxproc` type does not have a conversion.