diff --git a/flang/lib/Lower/OpenMP.cpp b/flang/lib/Lower/OpenMP.cpp
--- a/flang/lib/Lower/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP.cpp
@@ -138,11 +138,35 @@
   return converter.getFirOpBuilder().getIntegerType(loopVarTypeSize);
 }
 
+/// Create empty blocks for the current region.
+/// These blocks replace blocks parented to an enclosing region.
+void createEmptyRegionBlocks(
+    fir::FirOpBuilder &firOpBuilder,
+    std::list<Fortran::lower::pft::Evaluation> &evaluationList) {
+  auto *region = &firOpBuilder.getRegion();
+  for (auto &eval : evaluationList) {
+    if (eval.block) {
+      if (eval.block->empty()) {
+        eval.block->erase();
+        eval.block = firOpBuilder.createBlock(region);
+      } else {
+        [[maybe_unused]] auto &terminatorOp = eval.block->back();
+        assert((mlir::isa<mlir::omp::TerminatorOp>(terminatorOp) ||
+                mlir::isa<mlir::omp::YieldOp>(terminatorOp)) &&
+               "expected terminator op");
+      }
+    }
+    if (eval.hasNestedEvaluations())
+      createEmptyRegionBlocks(firOpBuilder, eval.getNestedEvaluations());
+  }
+}
+
 /// Create the body (block) for an OpenMP Operation.
 ///
 /// \param [in]    op - the operation the body belongs to.
 /// \param [inout] converter - converter to use for the clauses.
 /// \param [in]    loc - location in source code.
+/// \param [in]    eval - current PFT node/evaluation.
 /// \oaran [in]    clauses - list of clauses to process.
 /// \param [in]    args - block arguments (induction variable[s]) for the
 ////                      region.
@@ -151,14 +175,14 @@
 template <typename Op>
 static void
 createBodyOfOp(Op &op, Fortran::lower::AbstractConverter &converter,
-               mlir::Location &loc,
+               mlir::Location &loc, Fortran::lower::pft::Evaluation &eval,
                const Fortran::parser::OmpClauseList *clauses = nullptr,
                const SmallVector<const Fortran::semantics::Symbol *> &args = {},
                bool outerCombined = false) {
-  fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
-  // If arguments for the region are provided then create the block with those
-  // arguments. Also update the symbol's address with the mlir argument values.
-  // e.g. For loops the arguments are the induction variable. And all further
+  auto &firOpBuilder = converter.getFirOpBuilder();
+  // If an argument for the region is provided then create the block with that
+  // argument. Also update the symbol's address with the mlir argument value.
+  // e.g. For loops the argument is the induction variable. And all further
   // uses of the induction variable should use this mlir value.
   if (args.size()) {
     std::size_t loopVarTypeSize = 0;
@@ -184,7 +208,10 @@
   auto &block = op.getRegion().back();
   firOpBuilder.setInsertionPointToStart(&block);
 
-  // Insert the terminator.
+  if (eval.lowerAsUnstructured())
+    createEmptyRegionBlocks(firOpBuilder, eval.getNestedEvaluations());
+
+  // Ensure the block is well-formed by inserting terminators.
   if constexpr (std::is_same_v<Op, omp::WsLoopOp>) {
     mlir::ValueRange results;
     firOpBuilder.create<mlir::omp::YieldOp>(loc, results);
@@ -369,7 +396,7 @@
       allocateOperands, allocatorOperands, /*reduction_vars=*/ValueRange(),
       /*reductions=*/nullptr, procBindKindAttr);
 
-  createBodyOfOp<omp::ParallelOp>(parallelOp, converter, currentLocation,
+  createBodyOfOp<omp::ParallelOp>(parallelOp, converter, currentLocation, eval,
                                   &opClauseList, /*iv=*/{},
                                   /*isCombined=*/true);
 }
@@ -461,26 +488,27 @@
         allocateOperands, allocatorOperands, /*reduction_vars=*/ValueRange(),
         /*reductions=*/nullptr, procBindKindAttr);
     createBodyOfOp<omp::ParallelOp>(parallelOp, converter, currentLocation,
-                                    &opClauseList);
+                                    eval, &opClauseList);
   } else if (blockDirective.v == llvm::omp::OMPD_master) {
     auto masterOp =
         firOpBuilder.create<mlir::omp::MasterOp>(currentLocation, argTy);
-    createBodyOfOp<omp::MasterOp>(masterOp, converter, currentLocation);
+    createBodyOfOp<omp::MasterOp>(masterOp, converter, currentLocation, eval);
   } else if (blockDirective.v == llvm::omp::OMPD_single) {
     auto singleOp = firOpBuilder.create<mlir::omp::SingleOp>(
         currentLocation, allocateOperands, allocatorOperands, nowaitAttr);
-    createBodyOfOp<omp::SingleOp>(singleOp, converter, currentLocation);
+    createBodyOfOp<omp::SingleOp>(singleOp, converter, currentLocation, eval);
   } else if (blockDirective.v == llvm::omp::OMPD_ordered) {
     auto orderedOp = firOpBuilder.create<mlir::omp::OrderedRegionOp>(
         currentLocation, /*simd=*/nullptr);
-    createBodyOfOp<omp::OrderedRegionOp>(orderedOp, converter, currentLocation);
+    createBodyOfOp<omp::OrderedRegionOp>(orderedOp, converter, currentLocation,
+                                         eval);
   } else if (blockDirective.v == llvm::omp::OMPD_task) {
     auto taskOp = firOpBuilder.create<mlir::omp::TaskOp>(
         currentLocation, ifClauseOperand, finalClauseOperand, untiedAttr,
         mergeableAttr, /*in_reduction_vars=*/ValueRange(),
         /*in_reductions=*/nullptr, priorityClauseOperand, allocateOperands,
         allocatorOperands);
-    createBodyOfOp(taskOp, converter, currentLocation, &opClauseList);
+    createBodyOfOp(taskOp, converter, currentLocation, eval, &opClauseList);
   } else {
     TODO(converter.getCurrentLocation(), "Unhandled block directive");
   }
@@ -644,7 +672,7 @@
         wsLoopOp.nowaitAttr(firOpBuilder.getUnitAttr());
   }
 
-  createBodyOfOp<omp::WsLoopOp>(wsLoopOp, converter, currentLocation,
+  createBodyOfOp<omp::WsLoopOp>(wsLoopOp, converter, currentLocation, eval,
                                 &wsLoopOpClauseList, iv);
 }
 
@@ -688,7 +716,7 @@
                                firOpBuilder.getContext(), global.sym_name()));
     }
   }();
-  createBodyOfOp<omp::CriticalOp>(criticalOp, converter, currentLocation);
+  createBodyOfOp<omp::CriticalOp>(criticalOp, converter, currentLocation, eval);
 }
 
 static void
@@ -700,7 +728,7 @@
   auto currentLocation = converter.getCurrentLocation();
   mlir::omp::SectionOp sectionOp =
       firOpBuilder.create<mlir::omp::SectionOp>(currentLocation);
-  createBodyOfOp<omp::SectionOp>(sectionOp, converter, currentLocation);
+  createBodyOfOp<omp::SectionOp>(sectionOp, converter, currentLocation, eval);
 }
 
 // TODO: Add support for reduction
@@ -757,14 +785,15 @@
         currentLocation, /*reduction_vars*/ ValueRange(),
         /*reductions=*/nullptr, allocateOperands, allocatorOperands,
         /*nowait=*/nullptr);
-    createBodyOfOp(sectionsOp, converter, currentLocation);
+    createBodyOfOp(sectionsOp, converter, currentLocation, eval);
 
     // Sections Construct
   } else if (dir == llvm::omp::Directive::OMPD_sections) {
     auto sectionsOp = firOpBuilder.create<mlir::omp::SectionsOp>(
         currentLocation, reductionVars, /*reductions = */ nullptr,
         allocateOperands, allocatorOperands, noWaitClauseOperand);
-    createBodyOfOp<omp::SectionsOp>(sectionsOp, converter, currentLocation);
+    createBodyOfOp<omp::SectionsOp>(sectionsOp, converter, currentLocation,
+                                    eval);
   }
 }
 
diff --git a/flang/test/Lower/OpenMP/omp-unstructured.f90 b/flang/test/Lower/OpenMP/omp-unstructured.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Lower/OpenMP/omp-unstructured.f90
@@ -0,0 +1,113 @@
+! Test unstructured code adjacent to and inside OpenMP constructs.
+
+! RUN: bbc %s -fopenmp -o "-" | FileCheck %s
+
+! CHECK-LABEL: func @_QPss1{{.*}} {
+! CHECK:   br ^bb1
+! CHECK: ^bb1:  // 2 preds: ^bb0, ^bb3
+! CHECK:   cond_br %{{[0-9]*}}, ^bb2, ^bb4
+! CHECK: ^bb2:  // pred: ^bb1
+! CHECK:   cond_br %{{[0-9]*}}, ^bb4, ^bb3
+! CHECK: ^bb3:  // pred: ^bb2
+! CHECK:   @_FortranAioBeginExternalListOutput
+! CHECK:   br ^bb1
+! CHECK: ^bb4:  // 2 preds: ^bb1, ^bb2
+! CHECK:   omp.master  {
+! CHECK:     @_FortranAioBeginExternalListOutput
+! CHECK:     omp.terminator
+! CHECK:   }
+! CHECK:   @_FortranAioBeginExternalListOutput
+! CHECK: }
+subroutine ss1(n) ! unstructured code followed by a structured OpenMP construct
+  do i = 1, 3
+    if (i .eq. n) exit
+    print*, 'ss1-A', i
+  enddo
+  !$omp master
+    print*, 'ss1-B', i
+  !$omp end master
+  print*
+end
+
+! CHECK-LABEL: func @_QPss2{{.*}} {
+! CHECK:   omp.master  {
+! CHECK:     @_FortranAioBeginExternalListOutput
+! CHECK:     br ^bb1
+! CHECK:   ^bb1:  // 2 preds: ^bb0, ^bb3
+! CHECK:     cond_br %{{[0-9]*}}, ^bb2, ^bb4
+! CHECK:   ^bb2:  // pred: ^bb1
+! CHECK:     cond_br %{{[0-9]*}}, ^bb4, ^bb3
+! CHECK:   ^bb3:  // pred: ^bb2
+! CHECK:     @_FortranAioBeginExternalListOutput
+! CHECK:     br ^bb1
+! CHECK:   ^bb4:  // 2 preds: ^bb1, ^bb2
+! CHECK:     omp.terminator
+! CHECK:   }
+! CHECK:   @_FortranAioBeginExternalListOutput
+! CHECK:   @_FortranAioBeginExternalListOutput
+! CHECK: }
+subroutine ss2(n) ! unstructured OpenMP construct; loop exit inside construct
+  !$omp master
+    print*, 'ss2-A', n
+    do i = 1, 3
+      if (i .eq. n) exit
+      print*, 'ss2-B', i
+    enddo
+  !$omp end master
+  print*, 'ss2-C', i
+  print*
+end
+
+! CHECK-LABEL: func @_QPss3{{.*}} {
+! CHECK:   omp.parallel  {
+! CHECK:     br ^bb1
+! CHECK:   ^bb1:  // 2 preds: ^bb0, ^bb2
+! CHECK:     cond_br %{{[0-9]*}}, ^bb2, ^bb3
+! CHECK:   ^bb2:  // pred: ^bb1
+! CHECK:     omp.wsloop {{.*}} {
+! CHECK:     @_FortranAioBeginExternalListOutput
+! CHECK:       omp.yield
+! CHECK:     }
+! CHECK:     omp.wsloop {{.*}} {
+! CHECK:       br ^bb1
+! CHECK:     ^bb1:  // 2 preds: ^bb0, ^bb3
+! CHECK:       cond_br %{{[0-9]*}}, ^bb2, ^bb4
+! CHECK:     ^bb2:  // pred: ^bb1
+! CHECK:       cond_br %{{[0-9]*}}, ^bb4, ^bb3
+! CHECK:     ^bb3:  // pred: ^bb2
+! CHECK:       @_FortranAioBeginExternalListOutput
+! CHECK:       br ^bb1
+! CHECK:     ^bb4:  // 2 preds: ^bb1, ^bb2
+! CHECK:       omp.yield
+! CHECK:     }
+! CHECK:     br ^bb1
+! CHECK:   ^bb3:  // pred: ^bb1
+! CHECK:     omp.terminator
+! CHECK:   }
+! CHECK: }
+subroutine ss3(n) ! nested unstructured OpenMP constructs
+  !$omp parallel
+    do i = 1, 3
+      !$omp do
+        do k = 1, 3
+          print*, 'ss3-A', k
+        enddo
+      !$omp end do
+      !$omp do
+        do j = 1, 3
+          do k = 1, 3
+            if (k .eq. n) exit
+            print*, 'ss3-B', k
+          enddo
+        enddo
+      !$omp end do
+    enddo
+  !$omp end parallel
+end
+
+! CHECK-LABEL: func @_QQmain
+program p
+  call ss1(2)
+  call ss2(2)
+  call ss3(2)
+end