diff --git a/ArmPkg/ArmPkg.dec b/ArmPkg/ArmPkg.dec
index 99cb024d0f..f17ba913e6 100644
--- a/ArmPkg/ArmPkg.dec
+++ b/ArmPkg/ArmPkg.dec
@@ -71,6 +71,11 @@
   #
   ArmSvcLib|Include/Library/ArmSvcLib.h
 
+  ##  @libraryclass  Provides a Monitor Call interface that will use the
+  #   default conduit (HVC or SMC).
+  #
+  ArmMonitorLib|Include/Library/ArmMonitorLib.h
+
   ##  @libraryclass  Provides a default exception handler.
   #
   DefaultExceptionHandlerLib|Include/Library/DefaultExceptionHandlerLib.h
diff --git a/ArmPkg/Include/Library/ArmMonitorLib.h b/ArmPkg/Include/Library/ArmMonitorLib.h
new file mode 100644
index 0000000000..d6e13b61d6
--- /dev/null
+++ b/ArmPkg/Include/Library/ArmMonitorLib.h
@@ -0,0 +1,42 @@
+/** @file
+
+  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef ARM_MONITOR_LIB_H_
+#define ARM_MONITOR_LIB_H_
+
+/** The size of the SMC arguments is different between AArch64 and AArch32.
+
+  The native size is used for the arguments.
+  It will be casted to either HVC or SMC args.
+*/
+typedef struct {
+  UINTN    Arg0;
+  UINTN    Arg1;
+  UINTN    Arg2;
+  UINTN    Arg3;
+  UINTN    Arg4;
+  UINTN    Arg5;
+  UINTN    Arg6;
+  UINTN    Arg7;
+} ARM_MONITOR_ARGS;
+
+/** Monitor call.
+
+  An HyperVisor Call (HVC) or System Monitor Call (SMC) will be issued
+  depending on the default conduit. PcdMonitorConduitHvc determines the type
+  of the call: if true, do an HVC.
+
+  @param [in,out]  Args    Arguments for the HVC/SMC.
+**/
+VOID
+EFIAPI
+ArmMonitorCall (
+  IN OUT ARM_MONITOR_ARGS  *Args
+  );
+
+#endif // ARM_MONITOR_LIB_H_