diff --git a/trunk_lexer/src/lexer.rs b/trunk_lexer/src/lexer.rs
index d0377b0..a816f53 100644
--- a/trunk_lexer/src/lexer.rs
+++ b/trunk_lexer/src/lexer.rs
@@ -836,6 +836,7 @@ impl Lexer {
 #[allow(dead_code)]
 fn identifier_to_keyword(ident: &[u8]) -> Option<TokenKind> {
     Some(match ident {
+        b"readonly" => TokenKind::Readonly,
         b"global" => TokenKind::Global,
         b"match" => TokenKind::Match,
         b"abstract" => TokenKind::Abstract,
@@ -949,7 +950,7 @@ mod tests {
 
     #[test]
     fn keywords() {
-        assert_tokens("<?php function if else elseif echo return class extends implements public protected private static null NULL true TRUE false FALSE use const namespace interface new foreach instanceof", &[
+        assert_tokens("<?php function if else elseif echo return class extends implements public protected private static null NULL true TRUE false FALSE use const namespace interface new foreach instanceof readonly", &[
             open!(),
             TokenKind::Function,
             TokenKind::If,
@@ -977,6 +978,7 @@ mod tests {
             TokenKind::New,
             TokenKind::Foreach,
             TokenKind::Instanceof,
+            TokenKind::Readonly,
         ]);
     }
 
diff --git a/trunk_lexer/src/token.rs b/trunk_lexer/src/token.rs
index 4f3c2d9..51a598b 100644
--- a/trunk_lexer/src/token.rs
+++ b/trunk_lexer/src/token.rs
@@ -11,6 +11,7 @@ pub enum OpenTagKind {
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum TokenKind {
+    Readonly,
     Global,
     Abstract,
     Ampersand,
@@ -169,6 +170,7 @@ impl Default for Token {
 impl Display for TokenKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let s = match self {
+            Self::Readonly => "readonly",
             Self::AsteriskEqual => "*=",
             Self::ObjectCast => "(object)",
             Self::Abstract => "abstract",
diff --git a/trunk_parser/src/ast.rs b/trunk_parser/src/ast.rs
index e6cd1cd..8862704 100644
--- a/trunk_parser/src/ast.rs
+++ b/trunk_parser/src/ast.rs
@@ -118,6 +118,7 @@ impl From<TokenKind> for MethodFlag {
 pub enum ClassFlag {
     Final,
     Abstract,
+    Readonly,
 }
 
 impl From<TokenKind> for ClassFlag {
@@ -125,6 +126,7 @@ impl From<TokenKind> for ClassFlag {
         match k {
             TokenKind::Final => Self::Final,
             TokenKind::Abstract => Self::Abstract,
+            TokenKind::Readonly => Self::Readonly,
             _ => unreachable!("token {:?} can't be converted into class flag.", k),
         }
     }
diff --git a/trunk_parser/src/parser/mod.rs b/trunk_parser/src/parser/mod.rs
index e6b4547..c835051 100644
--- a/trunk_parser/src/parser/mod.rs
+++ b/trunk_parser/src/parser/mod.rs
@@ -416,6 +416,26 @@ impl Parser {
                     _ => unreachable!(),
                 }
             }
+            TokenKind::Readonly if self.peek.kind == TokenKind::Class => {
+                self.next();
+
+                match self.class()? {
+                    Statement::Class {
+                        name,
+                        extends,
+                        implements,
+                        body,
+                        ..
+                    } => Statement::Class {
+                        name,
+                        extends,
+                        implements,
+                        body,
+                        flag: Some(ClassFlag::Readonly),
+                    },
+                    _ => unreachable!(),
+                }
+            }
             TokenKind::Trait => {
                 self.next();
 
@@ -2193,8 +2213,8 @@ mod tests {
     use super::Parser;
     use crate::{
         ast::{
-            Arg, ArrayItem, Case, Constant, DeclareItem, ElseIf, IncludeKind, InfixOp, MethodFlag,
-            PropertyFlag,
+            Arg, ArrayItem, Case, ClassFlag, Constant, DeclareItem, ElseIf, IncludeKind, InfixOp,
+            MethodFlag, PropertyFlag,
         },
         Catch, Expression, Identifier, Param, Statement, Type,
     };
@@ -3515,6 +3535,20 @@ mod tests {
         )
     }
 
+    #[test]
+    fn readonly_classes() {
+        assert_ast(
+            "<?php readonly class Foo {}",
+            &[Statement::Class {
+                name: "Foo".as_bytes().into(),
+                extends: None,
+                implements: vec![],
+                body: vec![],
+                flag: Some(ClassFlag::Readonly),
+            }],
+        );
+    }
+
     fn assert_ast(source: &str, expected: &[Statement]) {
         let mut lexer = Lexer::new(None);
         let tokens = lexer.tokenize(source).unwrap();