diff --git a/MdePkg/Include/Uefi/UefiSpec.h b/MdePkg/Include/Uefi/UefiSpec.h
index 69c97bdb2a..fb464a405f 100644
--- a/MdePkg/Include/Uefi/UefiSpec.h
+++ b/MdePkg/Include/Uefi/UefiSpec.h
@@ -105,6 +105,16 @@ typedef enum {
 //
 #define EFI_MEMORY_CPU_CRYPTO  0x0000000000080000ULL
 
+//
+// If this flag is set, the memory region is present and capable of having
+// memory dynamically removed from the platform. This attribute serves as
+// a hint to the OS prior to its ACPI subsystem initialization to avoid
+// allocating this memory for core OS data or code that cannot be dynamically
+// relocated at runtime. If this flag is clear, the memory region is not
+// capable of being dynamically removed from the platform at runtime.
+//
+#define EFI_MEMORY_HOT_PLUGGABLE  0x0000000000100000
+
 //
 // Runtime memory attribute
 //