diff --git a/crates/oxc_transformer/src/react_jsx/mod.rs b/crates/oxc_transformer/src/react_jsx/mod.rs
index 52c89af79..3ad5edb16 100644
--- a/crates/oxc_transformer/src/react_jsx/mod.rs
+++ b/crates/oxc_transformer/src/react_jsx/mod.rs
@@ -8,7 +8,7 @@ use oxc_diagnostics::{
     miette::{self, Diagnostic},
     thiserror::Error,
 };
-use oxc_span::{Atom, SPAN};
+use oxc_span::{Atom, Span, SPAN};
 use oxc_syntax::{
     identifier::{is_irregular_whitespace, is_line_terminator},
     xml_entities::XML_ENTITIES,
@@ -22,6 +22,11 @@ use crate::context::TransformerCtx;
 #[diagnostic(severity(warning), help("Remove `pragma` and `pragmaFrag` options."))]
 struct PragmaAndPragmaFragCannotBeSet;
 
+#[derive(Debug, Error, Diagnostic)]
+#[error("Namespace tags are not supported by default. React's JSX doesn't support namespace tags. You can set `throwIfNamespace: false` to bypass this warning.")]
+#[diagnostic(severity(warning))]
+struct NamespaceDoesNotSupport(#[label] Span);
+
 /// Transform React JSX
 ///
 /// References:
@@ -519,7 +524,7 @@ impl<'a> ReactJsx<'a> {
         }
     }
 
-    fn transform_element_name(&self, name: &JSXElementName<'a>) -> Expression<'a> {
+    fn transform_element_name(&mut self, name: &JSXElementName<'a>) -> Expression<'a> {
         match name {
             JSXElementName::Identifier(ident) => {
                 let name = ident.name.clone();
@@ -533,11 +538,10 @@ impl<'a> ReactJsx<'a> {
                 self.transform_jsx_member_expression(member_expr)
             }
             JSXElementName::NamespacedName(name) => {
-                // TODO
-                // If the flag "throwIfNamespace" is false
-                // print XMLNamespace like string literal
-                // if self.options.throw_if_namespace.is_some_and(|v| !v) {
-                // }
+                if self.options.throw_if_namespace {
+                    self.ctx.error(NamespaceDoesNotSupport(name.span));
+                }
+
                 let string_literal = StringLiteral::new(SPAN, Atom::from(name.to_string()));
                 self.ast.literal_string_expression(string_literal)
             }
diff --git a/crates/oxc_transformer/src/react_jsx/options.rs b/crates/oxc_transformer/src/react_jsx/options.rs
index dd89d4266..5bc38fcde 100644
--- a/crates/oxc_transformer/src/react_jsx/options.rs
+++ b/crates/oxc_transformer/src/react_jsx/options.rs
@@ -10,7 +10,8 @@ pub struct ReactJsxOptions {
     pub runtime: ReactJsxRuntime,
     /// Toggles whether or not to throw an error if an XML namespaced tag name is used. e.g. `<f:image />`
     /// Though the JSX spec allows this, it is disabled by default since React's JSX does not currently have support for it.
-    pub throw_if_namespace: Option<bool>,
+    #[serde(default = "default_throw_if_namespace")]
+    pub throw_if_namespace: bool,
     /// Replaces the import source when importing functions. default to `react`
     #[serde(default = "default_import_source")]
     pub import_source: Cow<'static, str>,
@@ -26,6 +27,10 @@ pub struct ReactJsxOptions {
     pub pragma_frag: Cow<'static, str>,
 }
 
+fn default_throw_if_namespace() -> bool {
+    true
+}
+
 fn default_import_source() -> Cow<'static, str> {
     Cow::Borrowed("react")
 }
@@ -42,7 +47,7 @@ impl Default for ReactJsxOptions {
     fn default() -> Self {
         Self {
             runtime: ReactJsxRuntime::Classic,
-            throw_if_namespace: None,
+            throw_if_namespace: default_throw_if_namespace(),
             import_source: default_import_source(),
             pragma: default_pragma(),
             pragma_frag: default_pragma_frag(),
diff --git a/tasks/transform_conformance/babel.snap.md b/tasks/transform_conformance/babel.snap.md
index 16cf7dfd9..9f20b3eb5 100644
--- a/tasks/transform_conformance/babel.snap.md
+++ b/tasks/transform_conformance/babel.snap.md
@@ -1,4 +1,4 @@
-Passed: 267/1113
+Passed: 271/1113
 
 # All Passed:
 * babel-plugin-transform-numeric-separator
@@ -852,7 +852,7 @@ Passed: 267/1113
 * regression/11061/input.mjs
 * variable-declaration/non-null-in-optional-chain/input.ts
 
-# babel-plugin-transform-react-jsx (132/170)
+# babel-plugin-transform-react-jsx (136/170)
 * autoImport/after-polyfills-compiled-to-cjs/input.mjs
 * autoImport/complicated-scope-module/input.js
 * react/adds-appropriate-newlines-when-using-spread-attribute-babel-7/input.js
@@ -865,8 +865,6 @@ Passed: 267/1113
 * react/should-add-quotes-es3/input.js
 * react/should-disallow-spread-children/input.js
 * react/should-disallow-valueless-key/input.js
-* react/should-disallow-xml-namespacing/input.js
-* react/should-throw-error-namespaces-if-not-flag/input.js
 * react/should-warn-when-importSource-is-set/input.js
 * react/should-warn-when-importSource-pragma-is-set/input.js
 * react/wraps-props-in-react-spread-for-first-spread-attributes-babel-7/input.js
@@ -877,9 +875,7 @@ Passed: 267/1113
 * react-automatic/should-add-quotes-es3/input.js
 * react-automatic/should-disallow-spread-children/input.js
 * react-automatic/should-disallow-valueless-key/input.js
-* react-automatic/should-disallow-xml-namespacing/input.js
 * react-automatic/should-handle-attributed-elements/input.js
-* react-automatic/should-throw-error-namespaces-if-not-flag/input.js
 * react-automatic/should-throw-when-filter-is-specified/input.js
 * regression/issue-12478-automatic/input.js
 * regression/issue-12478-classic/input.js