Index: flang/lib/Lower/IO.cpp
===================================================================
--- flang/lib/Lower/IO.cpp
+++ flang/lib/Lower/IO.cpp
@@ -99,7 +99,7 @@
     mkIOKey(SetFile), mkIOKey(GetNewUnit), mkIOKey(GetSize),
     mkIOKey(GetIoLength), mkIOKey(GetIoMsg), mkIOKey(InquireCharacter),
     mkIOKey(InquireLogical), mkIOKey(InquirePendingId),
-    mkIOKey(InquireInteger64), mkIOKey(EndIoStatement)>
+    mkIOKey(InquireInteger64), mkIOKey(EndIoStatement), mkIOKey(SetConvert)>
     newIOTable;
 } // namespace Fortran::lower
 
@@ -983,7 +983,8 @@
     ioFunc = getIORuntimeFunc<mkIOKey(SetCarriagecontrol)>(loc, builder);
     break;
   case Fortran::parser::ConnectSpec::CharExpr::Kind::Convert:
-    TODO(loc, "CONVERT not part of the runtime::io interface");
+    ioFunc = getIORuntimeFunc<mkIOKey(SetConvert)>(loc, builder);
+    break;
   case Fortran::parser::ConnectSpec::CharExpr::Kind::Dispose:
     TODO(loc, "DISPOSE not part of the runtime::io interface");
   }
Index: flang/test/Lower/io-statement-open-options.f90
===================================================================
--- /dev/null
+++ flang/test/Lower/io-statement-open-options.f90
@@ -0,0 +1,12 @@
+! Test lowering of OPEN statment options
+! RUN: bbc %s -emit-fir -o - | FileCheck %s
+
+! CHECK-LABEL: func.func @_QPtest_convert_specifier(
+subroutine test_convert_specifier(unit)
+  integer :: unit
+  ! CHECK: %[[cookie:.*]] = fir.call @_FortranAioBeginOpenUnit(%{{.*}}, %{{.*}}, %{{.*}}) : (i32, !fir.ref<i8>, i32) -> !fir.ref<i8>
+  ! CHECK: %{{.*}} = fir.call @_FortranAioSetConvert(%[[cookie]], %{{.*}}, %{{.*}}) : (!fir.ref<i8>, !fir.ref<i8>, i64) -> i1
+  ! CHECK: %{{.*}} = fir.call @_FortranAioEndIoStatement(%[[cookie]]) : (!fir.ref<i8>) -> i32
+  open(unit, form="UNFORMATTED", convert="BIG_ENDIAN")
+  close(unit)
+end subroutine