diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -2912,6 +2912,7 @@
     {"sve2-sm4", {AArch64::FeatureSVE2SM4}},
     {"sve2-sha3", {AArch64::FeatureSVE2SHA3}},
     {"sve2-bitperm", {AArch64::FeatureSVE2BitPerm}},
+    {"ls64", {AArch64::FeatureLS64}},
     {"xs", {AArch64::FeatureXS}},
     // FIXME: Unsupported extensions
     {"pan", {}},
diff --git a/llvm/test/MC/AArch64/directive-arch_extension-negative.s b/llvm/test/MC/AArch64/directive-arch_extension-negative.s
--- a/llvm/test/MC/AArch64/directive-arch_extension-negative.s
+++ b/llvm/test/MC/AArch64/directive-arch_extension-negative.s
@@ -83,3 +83,8 @@
 ldapr x0, [x1]
 // CHECK: error: instruction requires: rcpc
 // CHECK-NEXT: ldapr x0, [x1]
+
+.arch_extension nols64
+ld64b x0, [x13]
+// CHECK: error: instruction requires: ls64
+// CHECK-NEXT: ld64b x0, [x13]
diff --git a/llvm/test/MC/AArch64/directive-arch_extension.s b/llvm/test/MC/AArch64/directive-arch_extension.s
--- a/llvm/test/MC/AArch64/directive-arch_extension.s
+++ b/llvm/test/MC/AArch64/directive-arch_extension.s
@@ -67,3 +67,7 @@
 .arch_extension rcpc
 ldapr x0, [x1]
 // CHECK: ldapr x0, [x1]
+
+.arch_extension ls64
+ld64b x0, [x13]
+// CHECK: ld64b x0, [x13]