diff --git a/parser/src/parser/cst2ast.rs b/parser/src/parser/cst2ast.rs
index 7045e709e..6e0d1e0b7 100644
--- a/parser/src/parser/cst2ast.rs
+++ b/parser/src/parser/cst2ast.rs
@@ -1774,6 +1774,9 @@ where
     let mut literal = integer_lit.as_str();
     let mut multiplier = 1;
 
+    let without_underscore = literal.replace('_', "");
+    literal = without_underscore.as_str();
+
     if let Some(without_suffix) = literal.strip_suffix("KB") {
         literal = without_suffix;
         multiplier = 1024;
@@ -1833,9 +1836,12 @@ fn float_lit_from_cst<'src>(
 ) -> Result<f64, Error> {
     expect!(float_lit, GrammarRule::float_lit);
 
-    let literal = float_lit.as_str();
+    let mut literal = float_lit.as_str();
     let span = ctx.span(&float_lit);
 
+    let without_underscore = literal.replace('_', "");
+    literal = without_underscore.as_str();
+
     literal.parse::<f64>().map_err(|err| {
         Error::from(ErrorInfo::invalid_float(
             ctx.report_builder,
diff --git a/parser/src/parser/grammar.pest b/parser/src/parser/grammar.pest
index 7141e5e2b..142cf0353 100644
--- a/parser/src/parser/grammar.pest
+++ b/parser/src/parser/grammar.pest
@@ -277,13 +277,13 @@ string_lit = @{
 }
 
 integer_lit = @{
-  "-"? ~ "0x" ~ ASCII_HEX_DIGIT+ |
-  "-"? ~ "0o" ~ ASCII_OCT_DIGIT+ |
-  "-"? ~ ASCII_DIGIT+ ~ ("KB" | "MB")?
+  "-"? ~ "0x" ~ ASCII_HEX_DIGIT+ ~ ("_" | ASCII_HEX_DIGIT)* |
+  "-"? ~ "0o" ~ ASCII_OCT_DIGIT+ ~ ("_" | ASCII_OCT_DIGIT)* |
+  "-"? ~ ASCII_DIGIT+ ~ ("_" | ASCII_DIGIT)* ~ ("KB" | "MB")?
 }
 
 float_lit = @{
-  "-"? ~ ASCII_DIGIT+ ~ DOT ~ ASCII_DIGIT+
+  "-"? ~ ASCII_DIGIT+ ~ ("_" | ASCII_DIGIT)* ~ DOT ~ ASCII_DIGIT+ ~ ("_" | ASCII_DIGIT)*
 }
 
 regexp = @{
diff --git a/parser/src/parser/tests/cst.rs b/parser/src/parser/tests/cst.rs
index 484d84259..8a2a25b8c 100644
--- a/parser/src/parser/tests/cst.rs
+++ b/parser/src/parser/tests/cst.rs
@@ -985,6 +985,109 @@ rule test : foo bar baz {
        │  └─ ident "baz"
        ├─ LPAREN "("
        └─ RPAREN ")"
+"#,
+        ),
+        ////////////////////////////////////////////////////////////
+        (
+            line!(),
+            GrammarRule::term,
+            r#"#a in (1_000..200_)"#,
+            r##"
+ term
+ └─ primary_expr
+    ├─ pattern_count "#a"
+    ├─ k_IN "in"
+    └─ range
+       ├─ LPAREN "("
+       ├─ expr
+       │  └─ term
+       │     └─ primary_expr
+       │        └─ integer_lit "1_000"
+       ├─ DOT_DOT ".."
+       ├─ expr
+       │  └─ term
+       │     └─ primary_expr
+       │        └─ integer_lit "200_"
+       └─ RPAREN ")"
+"##,
+        ),
+        ////////////////////////////////////////////////////////////
+        (
+            line!(),
+            GrammarRule::expr,
+            r#"0x0_2 | 0o00_1 & 0x03_"#,
+            r#"
+ expr
+ ├─ term
+ │  └─ primary_expr
+ │     └─ integer_lit "0x0_2"
+ ├─ BITWISE_OR "|"
+ ├─ term
+ │  └─ primary_expr
+ │     └─ integer_lit "0o00_1"
+ ├─ BITWISE_AND "&"
+ └─ term
+    └─ primary_expr
+       └─ integer_lit "0x03_"
+"#,
+        ),
+        ////////////////////////////////////////////////////////////
+        (
+            line!(),
+            GrammarRule::expr,
+            r#"0_2_2 | 0x00000_11 & 0o05_5"#,
+            r#"
+ expr
+ ├─ term
+ │  └─ primary_expr
+ │     └─ integer_lit "0_2_2"
+ ├─ BITWISE_OR "|"
+ ├─ term
+ │  └─ primary_expr
+ │     └─ integer_lit "0x00000_11"
+ ├─ BITWISE_AND "&"
+ └─ term
+    └─ primary_expr
+       └─ integer_lit "0o05_5"
+"#,
+        ),
+        ////////////////////////////////////////////////////////////
+        (
+            line!(),
+            GrammarRule::boolean_expr,
+            r#"2.5_5 * 2__3 * -1.0_1 == 5_55.05 + -(1_1)"#,
+            r#"
+ boolean_expr
+ └─ boolean_term
+    ├─ expr
+    │  ├─ term
+    │  │  └─ primary_expr
+    │  │     └─ float_lit "2.5_5"
+    │  ├─ MUL "*"
+    │  ├─ term
+    │  │  └─ primary_expr
+    │  │     └─ integer_lit "2__3"
+    │  ├─ MUL "*"
+    │  └─ term
+    │     └─ primary_expr
+    │        └─ float_lit "-1.0_1"
+    ├─ EQ "=="
+    └─ expr
+       ├─ term
+       │  └─ primary_expr
+       │     └─ float_lit "5_55.05"
+       ├─ ADD "+"
+       └─ term
+          └─ primary_expr
+             ├─ MINUS "-"
+             └─ term
+                └─ primary_expr
+                   ├─ LPAREN "("
+                   ├─ expr
+                   │  └─ term
+                   │     └─ primary_expr
+                   │        └─ integer_lit "1_1"
+                   └─ RPAREN ")"
 "#,
         ),
     ];
diff --git a/parser/src/parser/tests/testdata/literals.yaml b/parser/src/parser/tests/testdata/literals.yaml
index 6dc8ce56d..badfc2be4 100644
--- a/parser/src/parser/tests/testdata/literals.yaml
+++ b/parser/src/parser/tests/testdata/literals.yaml
@@ -118,4 +118,19 @@
              ├─ 1MB
              └─ 1024KB
 
+###############################################################################
+
+- rule: |
+    rule test {
+      condition:
+        1_000MB == 10_24KB
+    }
+  ast: |
+    root
+    └─ rule test
+       └─ condition
+          └─ eq
+             ├─ 1_000MB
+             └─ 10_24KB
+
 ###############################################################################
\ No newline at end of file