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
@@ -22,12 +22,21 @@
 #include "mlir/IR/Matchers.h"
 #include "mlir/Pass/Pass.h"
 #include "llvm/ADT/ArrayRef.h"
+#include <mlir/Dialect/LLVMIR/LLVMDialect.h>
 
 #define DEBUG_TYPE "flang-codegen"
 
 // fir::LLVMTypeConverter for converting to LLVM IR dialect types.
 #include "TypeConverter.h"
 
+static mlir::LLVM::ConstantOp
+genConstantIndex(mlir::Location loc, mlir::Type ity,
+                 mlir::ConversionPatternRewriter &rewriter,
+                 std::int64_t offset) {
+  auto cattr = rewriter.getI64IntegerAttr(offset);
+  return rewriter.create<mlir::LLVM::ConstantOp>(loc, ity, cattr);
+}
+
 namespace {
 /// FIR conversion pattern template
 template <typename FromOp>
@@ -65,6 +74,34 @@
             mlir::ConversionPatternRewriter &rewriter) const = 0;
 };
 
+// Create value signaling an absent optional argument in a call, e.g.
+// `fir.absent !fir.ref<i64>` -->  `llvm.mlir.null : !llvm.ptr<i64>`
+struct AbsentOpConversion : public FIROpConversion<fir::AbsentOp> {
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::AbsentOp absent, OpAdaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    mlir::Type ty = convertType(absent.getType());
+    mlir::Location loc = absent.getLoc();
+
+    if (absent.getType().isa<fir::BoxCharType>()) {
+      auto structTy = ty.cast<mlir::LLVM::LLVMStructType>();
+      assert(!structTy.isOpaque() && !structTy.getBody().empty());
+      auto undefStruct = rewriter.create<mlir::LLVM::UndefOp>(loc, ty);
+      auto nullField =
+          rewriter.create<mlir::LLVM::NullOp>(loc, structTy.getBody()[0]);
+      mlir::MLIRContext *ctx = absent.getContext();
+      auto c0 = mlir::ArrayAttr::get(ctx, rewriter.getI32IntegerAttr(0));
+      rewriter.replaceOpWithNewOp<mlir::LLVM::InsertValueOp>(
+          absent, ty, undefStruct, nullField, c0);
+    } else {
+      rewriter.replaceOpWithNewOp<mlir::LLVM::NullOp>(absent, ty);
+    }
+    return success();
+  }
+};
+
 // Lower `fir.address_of` operation to `llvm.address_of` operation.
 struct AddrOfOpConversion : public FIROpConversion<fir::AddrOfOp> {
   using FIROpConversion::FIROpConversion;
@@ -487,6 +524,41 @@
     return success();
   }
 };
+
+// `fir.is_present` -->
+// ```
+//  %0 = llvm.mlir.constant(0 : i64)
+//  %1 = llvm.ptrtoint %0
+//  %2 = llvm.icmp "ne" %1, %0 : i64
+// ```
+struct IsPresentOpConversion : public FIROpConversion<fir::IsPresentOp> {
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::IsPresentOp isPresent, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    mlir::Type idxTy = lowerTy().indexType();
+    mlir::Location loc = isPresent.getLoc();
+    auto ptr = adaptor.getOperands()[0];
+
+    if (isPresent.val().getType().isa<fir::BoxCharType>()) {
+      auto structTy = ptr.getType().cast<mlir::LLVM::LLVMStructType>();
+      assert(!structTy.isOpaque() && !structTy.getBody().empty());
+
+      mlir::Type ty = structTy.getBody()[0];
+      mlir::MLIRContext *ctx = isPresent.getContext();
+      auto c0 = mlir::ArrayAttr::get(ctx, rewriter.getI32IntegerAttr(0));
+      ptr = rewriter.create<mlir::LLVM::ExtractValueOp>(loc, ty, ptr, c0);
+    }
+    mlir::LLVM::ConstantOp c0 =
+        genConstantIndex(isPresent.getLoc(), idxTy, rewriter, 0);
+    auto addr = rewriter.create<mlir::LLVM::PtrToIntOp>(loc, idxTy, ptr);
+    rewriter.replaceOpWithNewOp<mlir::LLVM::ICmpOp>(
+        isPresent, mlir::LLVM::ICmpPredicate::ne, addr, c0);
+
+    return success();
+  }
+};
 } // namespace
 
 namespace {
@@ -504,12 +576,13 @@
     auto *context = getModule().getContext();
     fir::LLVMTypeConverter typeConverter{getModule()};
     mlir::OwningRewritePatternList pattern(context);
-    pattern.insert<
-        AddrOfOpConversion, CallOpConversion, ExtractValueOpConversion,
-        HasValueOpConversion, GlobalOpConversion, InsertOnRangeOpConversion,
-        InsertValueOpConversion, SelectOpConversion, SelectRankOpConversion,
-        UndefOpConversion, UnreachableOpConversion, ZeroOpConversion>(
-        typeConverter);
+    pattern
+        .insert<AbsentOpConversion, AddrOfOpConversion, CallOpConversion,
+                ExtractValueOpConversion, HasValueOpConversion,
+                GlobalOpConversion, InsertOnRangeOpConversion,
+                InsertValueOpConversion, IsPresentOpConversion,
+                SelectOpConversion, SelectRankOpConversion, 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
@@ -47,6 +47,9 @@
     });
   }
 
+  // i64 can be used to index into aggregates like arrays
+  mlir::Type indexType() { return mlir::IntegerType::get(&getContext(), 64); }
+
   // fir.type<name(p : TY'...){f : TY...}>  -->  llvm<"%name = { ty... }">
   mlir::Type convertRecordType(fir::RecordType derived) {
     auto name = derived.getName();
diff --git a/flang/test/Fir/convert-to-llvm.fir b/flang/test/Fir/convert-to-llvm.fir
--- a/flang/test/Fir/convert-to-llvm.fir
+++ b/flang/test/Fir/convert-to-llvm.fir
@@ -325,6 +325,7 @@
 // CHECK:         llvm.return
 
 // -----
+
 // Test `fir.call` -> `llvm.call` conversion for functions that take no arguments
 // and return nothing
 
@@ -376,3 +377,33 @@
 // CHECK-NEXT:    %0 = llvm.call @dummy_return_val() : () -> i32
 // CHECK-NEXT:    llvm.return %0 : i32
 // CHECK-NEXT:  }
+
+// -----
+
+// Test `fir.is_present` and `fir.absent`
+
+func @present(%arg0: !fir.ref<i64>) -> i1 {
+  %0 = fir.is_present %arg0 : (!fir.ref<i64>) -> i1
+  return %0 : i1
+}
+
+// CHECK-LABEL: @present
+// CHECK-SAME: (%[[arg:.*]]: !llvm.ptr<i64>) -> i1
+// CHECK-NEXT:  %[[constant:.*]] = llvm.mlir.constant(0 : i64) : i64
+// CHECK-NEXT:  %[[ptr:.*]] = llvm.ptrtoint %[[arg]] : !llvm.ptr<i64> to i64
+// CHECK-NEXT:  %[[ret_val:.*]] = llvm.icmp "ne" %[[ptr]], %[[constant]] : i64
+// CHECK-NEXT:  llvm.return %[[ret_val]] : i1
+// CHECK-NEXT: }
+
+func @absent() -> i1 {
+  %0 = fir.absent !fir.ref<i64>
+  %1 = fir.call @present(%0) : (!fir.ref<i64>) -> i1
+  return %1 : i1
+}
+
+// CHECK-LABEL: @absent
+// CHECK-SAME:  () -> i1
+// CHECK-NEXT:  %[[ptr:.*]] = llvm.mlir.null : !llvm.ptr<i64>
+// CHECK-NEXT:  %[[ret_val:.*]] = llvm.call @present(%[[ptr]]) : (!llvm.ptr<i64>) -> i1
+// CHECK-NEXT:  llvm.return %[[ret_val]] : i1
+// CHECK-NEXT:  }