diff --git a/js/src/builtin/TestingFunctions.cpp b/js/src/builtin/TestingFunctions.cpp
index 7c9079e0d46a..315ce01fe063 100644
--- a/js/src/builtin/TestingFunctions.cpp
+++ b/js/src/builtin/TestingFunctions.cpp
@@ -4990,24 +4990,6 @@ SetTimeResolution(JSContext* cx, unsigned argc, Value* vp)
    return true;
 }
 
-static bool
-EnableExpressionClosures(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-    JS::ContextOptionsRef(cx).setExpressionClosures(true);
-    args.rval().setUndefined();
-    return true;
-}
-
-static bool
-DisableExpressionClosures(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-    JS::ContextOptionsRef(cx).setExpressionClosures(false);
-    args.rval().setUndefined();
-    return true;
-}
-
 JSScript*
 js::TestingFunctionArgumentToScript(JSContext* cx,
                                     HandleValue v,
@@ -5781,14 +5763,6 @@ gc::ZealModeHelpText),
 "  Enables time clamping and jittering. Specify a time resolution in\n"
 "  microseconds and whether or not to jitter\n"),
 
-    JS_FN_HELP("enableExpressionClosures", EnableExpressionClosures, 0, 0,
-"enableExpressionClosures()",
-"  Enables the deprecated, non-standard expression closures.\n"),
-
-    JS_FN_HELP("disableExpressionClosures", DisableExpressionClosures, 0, 0,
-"disableExpressionClosures()",
-"  Disables the deprecated, non-standard expression closures.\n"),
-
     JS_FN_HELP("baselineCompile", BaselineCompile, 2, 0,
 "baselineCompile([fun/code], forceDebugInstrumentation=false)",
 "  Baseline-compiles the given JS function or script.\n"
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 82bbf22c00a8..673e7ebbe2cd 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -3262,16 +3262,6 @@ Parser<FullParseHandler, CharT>::skipLazyInnerFunction(ParseNode* funcNode, uint
     if (!tokenStream.advance(fun->lazyScript()->end()))
         return false;
 
-    if (allowExpressionClosures()) {
-        // Only expression closure can be Statement kind.
-        // If we remove expression closure, we can remove isExprBody flag from
-        // LazyScript and JSScript.
-        if (kind == Statement && funbox->isExprBody()) {
-            if (!matchOrInsertSemicolon())
-                return false;
-        }
-    }
-
     // Append possible Annex B function box only upon successfully parsing.
     if (tryAnnexB && !pc->innermostScope()->addPossibleAnnexBFunctionBox(pc, funbox))
         return false;
@@ -3785,23 +3775,8 @@ GeneralParser<ParseHandler, CharT>::functionFormalParametersAndBody(InHandling i
     uint32_t openedPos = 0;
     if (tt != TokenKind::Lc) {
         if (kind != Arrow) {
-            if (funbox->isGenerator() || funbox->isAsync() || kind == Method ||
-                kind == GetterNoExpressionClosure || kind == SetterNoExpressionClosure ||
-                IsConstructorKind(kind) || kind == PrimaryExpression)
-            {
-                error(JSMSG_CURLY_BEFORE_BODY);
-                return false;
-            }
-
-            if (allowExpressionClosures()) {
-                this->addTelemetry(DeprecatedLanguageExtension::ExpressionClosure);
-                if (!warnOnceAboutExprClosure())
-                    return false;
-                handler.noteExpressionClosure(pn);
-            } else {
-                error(JSMSG_CURLY_BEFORE_BODY);
-                return false;
-            }
+            error(JSMSG_CURLY_BEFORE_BODY);
+            return false;
         }
 
         anyChars.ungetToken();
@@ -3863,7 +3838,7 @@ GeneralParser<ParseHandler, CharT>::functionFormalParametersAndBody(InHandling i
                                                               JSMSG_CURLY_OPENED, openedPos));
         funbox->setEnd(anyChars);
     } else {
-        MOZ_ASSERT_IF(!allowExpressionClosures(), kind == Arrow);
+        MOZ_ASSERT(kind == Arrow);
 
         if (anyChars.hadError())
             return false;
diff --git a/js/src/frontend/Parser.h b/js/src/frontend/Parser.h
index df4ead910f54..d01bfd1d1256 100644
--- a/js/src/frontend/Parser.h
+++ b/js/src/frontend/Parser.h
@@ -340,9 +340,6 @@ class ParserBase
 
     bool hasValidSimpleStrictParameterNames();
 
-    bool allowExpressionClosures() const {
-        return options().expressionClosuresOption;
-    }
     /*
      * Create a new function object given a name (which is optional if this is
      * a function expression).
@@ -705,7 +702,6 @@ class GeneralParser
     using Base::isValidSimpleAssignmentTarget;
     using Base::pc;
     using Base::usedNames;
-    using Base::allowExpressionClosures;
 
   private:
     using Base::checkAndMarkSuperScope;
@@ -1408,7 +1404,6 @@ class Parser<FullParseHandler, CharT> final
     using Base::pos;
     using Base::ss;
     using Base::tokenStream;
-    using Base::allowExpressionClosures;
 
   private:
     using Base::alloc;
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 4dcee8f8c1a5..580b356bb583 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -3965,7 +3965,6 @@ JS::TransitiveCompileOptions::copyPODTransitiveOptions(const TransitiveCompileOp
     canLazilyParse = rhs.canLazilyParse;
     strictOption = rhs.strictOption;
     extraWarningsOption = rhs.extraWarningsOption;
-    expressionClosuresOption = rhs.expressionClosuresOption;
     werrorOption = rhs.werrorOption;
     asmJSOption = rhs.asmJSOption;
     throwOnAsmJSValidationFailureOption = rhs.throwOnAsmJSValidationFailureOption;
@@ -4088,7 +4087,6 @@ JS::CompileOptions::CompileOptions(JSContext* cx)
 {
     strictOption = cx->options().strictMode();
     extraWarningsOption = cx->compartment()->behaviors().extraWarnings(cx);
-    expressionClosuresOption = cx->options().expressionClosures();
     isProbablySystemCode = cx->compartment()->isProbablySystemCode();
     werrorOption = cx->options().werror();
     if (!cx->options().asmJS())
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 2dec365467d0..ac78516174ef 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -990,7 +990,6 @@ class JS_PUBLIC_API(ContextOptions) {
 #ifdef FUZZING
         , fuzzing_(false)
 #endif
-        , expressionClosures_(false)
         , arrayProtoValues_(true)
     {
     }
@@ -1147,12 +1146,6 @@ class JS_PUBLIC_API(ContextOptions) {
     }
 #endif
 
-    bool expressionClosures() const { return expressionClosures_; }
-    ContextOptions& setExpressionClosures(bool flag) {
-        expressionClosures_ = flag;
-        return *this;
-    }
-
     bool arrayProtoValues() const { return arrayProtoValues_; }
     ContextOptions& setArrayProtoValues(bool flag) {
         arrayProtoValues_ = flag;
@@ -1189,7 +1182,6 @@ class JS_PUBLIC_API(ContextOptions) {
 #ifdef FUZZING
     bool fuzzing_ : 1;
 #endif
-    bool expressionClosures_ : 1;
     bool arrayProtoValues_ : 1;
 
 };
@@ -3591,7 +3583,6 @@ class JS_FRIEND_API(TransitiveCompileOptions)
         canLazilyParse(true),
         strictOption(false),
         extraWarningsOption(false),
-        expressionClosuresOption(false),
         werrorOption(false),
         asmJSOption(AsmJSOption::Disabled),
         throwOnAsmJSValidationFailureOption(false),
@@ -3627,7 +3618,6 @@ class JS_FRIEND_API(TransitiveCompileOptions)
     bool canLazilyParse;
     bool strictOption;
     bool extraWarningsOption;
-    bool expressionClosuresOption;
     bool werrorOption;
     AsmJSOption asmJSOption;
     bool throwOnAsmJSValidationFailureOption;