diff --git a/boa/src/builtins/function/mod.rs b/boa/src/builtins/function/mod.rs
index 5e7a5ae973..ae4575c1c6 100644
--- a/boa/src/builtins/function/mod.rs
+++ b/boa/src/builtins/function/mod.rs
@@ -429,7 +429,22 @@ pub fn make_constructor_fn(
     constructor_val
 }
 
-/// Macro to create a new member function of a prototype.
+/// Creates a new member function of a `Object` or `prototype`.
+///
+/// A function registered using this macro can then be called from Javascript using:
+///
+/// parent.name()
+///
+/// See the javascript 'Number.toString()' as an example.
+///
+/// # Arguments
+/// function: The function to register as a built in function.
+/// name: The name of the function (how it will be called but without the ()).
+/// parent: The object to register the function on, if the global object is used then the function is instead called as name()
+///     without requiring the parent, see parseInt() as an example.
+/// length: As described at https://tc39.es/ecma262/#sec-function-instances-length, The value of the "length" property is an integer that
+///     indicates the typical number of arguments expected by the function. However, the language permits the function to be invoked with
+///     some other number of arguments.
 ///
 /// If no length is provided, the length will be set to 0.
 pub fn make_builtin_fn<N>(function: NativeFunctionData, name: N, parent: &Value, length: i32)
diff --git a/boa/src/builtins/number/mod.rs b/boa/src/builtins/number/mod.rs
index 86ee9d4344..b2cd26b5f7 100644
--- a/boa/src/builtins/number/mod.rs
+++ b/boa/src/builtins/number/mod.rs
@@ -37,6 +37,12 @@ const BUF_SIZE: usize = 2200;
 #[derive(Debug, Clone, Copy)]
 pub(crate) struct Number;
 
+/// Maximum number of arguments expected to the builtin parseInt() function.
+const PARSE_INT_MAX_ARG_COUNT: usize = 2;
+
+/// Maximum number of arguments expected to the builtin parseFloat() function.
+const PARSE_FLOAT_MAX_ARG_COUNT: usize = 1;
+
 impl Number {
     /// Helper function that converts a Value to a Number.
     #[allow(clippy::wrong_self_convention)]
@@ -405,6 +411,122 @@ impl Number {
         Ok(Self::to_number(this))
     }
 
+    /// Builtin javascript 'parseInt(str, radix)' function.
+    ///
+    /// Parses the given string as an integer using the given radix as a base.
+    ///
+    /// An argument of type Number (i.e. Integer or Rational) is also accepted in place of string.
+    ///
+    /// The radix must be an integer in the range [2, 36] inclusive.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-parseint-string-radix
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt
+    pub(crate) fn parse_int(
+        _this: &mut Value,
+        args: &[Value],
+        _ctx: &mut Interpreter,
+    ) -> ResultValue {
+        if let (Some(val), r) = (args.get(0), args.get(1)) {
+            let mut radix = if let Some(rx) = r {
+                if let ValueData::Integer(i) = rx.data() {
+                    *i as u32
+                } else {
+                    // Handling a second argument that isn't an integer but was provided so cannot be defaulted.
+                    return Ok(Value::from(f64::NAN));
+                }
+            } else {
+                // No second argument provided therefore radix is unknown
+                0
+            };
+
+            match val.data() {
+                ValueData::String(s) => {
+                    // Attempt to infer radix from given string.
+
+                    if radix == 0 {
+                        if s.starts_with("0x") || s.starts_with("0X") {
+                            if let Ok(i) = i32::from_str_radix(&s[2..], 16) {
+                                return Ok(Value::integer(i));
+                            } else {
+                                // String can't be parsed.
+                                return Ok(Value::from(f64::NAN));
+                            }
+                        } else {
+                            radix = 10
+                        };
+                    }
+
+                    if let Ok(i) = i32::from_str_radix(s, radix) {
+                        Ok(Value::integer(i))
+                    } else {
+                        // String can't be parsed.
+                        Ok(Value::from(f64::NAN))
+                    }
+                }
+                ValueData::Integer(i) => Ok(Value::integer(*i)),
+                ValueData::Rational(f) => Ok(Value::integer(*f as i32)),
+                _ => {
+                    // Wrong argument type to parseInt.
+                    Ok(Value::from(f64::NAN))
+                }
+            }
+        } else {
+            // Not enough arguments to parseInt.
+            Ok(Value::from(f64::NAN))
+        }
+    }
+
+    /// Builtin javascript 'parseFloat(str)' function.
+    ///
+    /// Parses the given string as a floating point value.
+    ///
+    /// An argument of type Number (i.e. Integer or Rational) is also accepted in place of string.
+    ///
+    /// To improve performance an Integer type Number is returned in place of a Rational if the given
+    /// string can be parsed and stored as an Integer.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-parsefloat-string
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat
+    pub(crate) fn parse_float(
+        _this: &mut Value,
+        args: &[Value],
+        _ctx: &mut Interpreter,
+    ) -> ResultValue {
+        if let Some(val) = args.get(0) {
+            match val.data() {
+                ValueData::String(s) => {
+                    if let Ok(i) = s.parse::<i32>() {
+                        // Attempt to parse an integer first so that it can be stored as an integer
+                        // to improve performance
+                        Ok(Value::integer(i))
+                    } else if let Ok(f) = s.parse::<f64>() {
+                        Ok(Value::rational(f))
+                    } else {
+                        // String can't be parsed.
+                        Ok(Value::from(f64::NAN))
+                    }
+                }
+                ValueData::Integer(i) => Ok(Value::integer(*i)),
+                ValueData::Rational(f) => Ok(Value::rational(*f)),
+                _ => {
+                    // Wrong argument type to parseFloat.
+                    Ok(Value::from(f64::NAN))
+                }
+            }
+        } else {
+            // Not enough arguments to parseFloat.
+            Ok(Value::from(f64::NAN))
+        }
+    }
+
     /// Create a new `Number` object
     pub(crate) fn create(global: &Value) -> Value {
         let prototype = Value::new_object(Some(global));
@@ -417,6 +539,19 @@ impl Number {
         make_builtin_fn(Self::to_string, "toString", &prototype, 1);
         make_builtin_fn(Self::value_of, "valueOf", &prototype, 0);
 
+        make_builtin_fn(
+            Self::parse_int,
+            "parseInt",
+            global,
+            PARSE_INT_MAX_ARG_COUNT as i32,
+        );
+        make_builtin_fn(
+            Self::parse_float,
+            "parseFloat",
+            global,
+            PARSE_FLOAT_MAX_ARG_COUNT as i32,
+        );
+
         let number = make_constructor_fn("Number", 1, Self::make_number, global, prototype, true);
 
         // Constants from:
diff --git a/boa/src/builtins/number/tests.rs b/boa/src/builtins/number/tests.rs
index 090f9f180e..c1a310764c 100644
--- a/boa/src/builtins/number/tests.rs
+++ b/boa/src/builtins/number/tests.rs
@@ -470,3 +470,210 @@ fn number_constants() {
         .unwrap()
         .is_null_or_undefined());
 }
+
+#[test]
+fn parse_int_simple() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"6\")"), "6");
+}
+
+#[test]
+fn parse_int_negative() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"-9\")"), "-9");
+}
+
+#[test]
+fn parse_int_already_int() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(100)"), "100");
+}
+
+#[test]
+fn parse_int_float() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(100.5)"), "100");
+}
+
+#[test]
+fn parse_int_float_str() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"100.5\")"), "NaN");
+}
+
+#[test]
+fn parse_int_inferred_hex() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"0xA\")"), "10");
+}
+
+/// This test demonstrates that this version of parseInt treats strings starting with 0 to be parsed with
+/// a radix 10 if no radix is specified. Some alternative implementations default to a radix of 8.
+#[test]
+fn parse_int_zero_start() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"018\")"), "18");
+}
+
+#[test]
+fn parse_int_varying_radix() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    let base_str = "1000";
+
+    for radix in 2..36 {
+        let expected = i32::from_str_radix(base_str, radix).unwrap();
+
+        assert_eq!(
+            forward(
+                &mut engine,
+                &format!("parseInt(\"{}\", {} )", base_str, radix)
+            ),
+            expected.to_string()
+        );
+    }
+}
+
+#[test]
+fn parse_int_negative_varying_radix() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    let base_str = "-1000";
+
+    for radix in 2..36 {
+        let expected = i32::from_str_radix(base_str, radix).unwrap();
+
+        assert_eq!(
+            forward(
+                &mut engine,
+                &format!("parseInt(\"{}\", {} )", base_str, radix)
+            ),
+            expected.to_string()
+        );
+    }
+}
+
+#[test]
+fn parse_int_malformed_str() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"hello\")"), "NaN");
+}
+
+#[test]
+fn parse_int_undefined() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(undefined)"), "NaN");
+}
+
+/// Shows that no arguments to parseInt is treated the same as if undefined was
+/// passed as the first argument.
+#[test]
+fn parse_int_no_args() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt()"), "NaN");
+}
+
+/// Shows that extra arguments to parseInt are ignored.
+#[test]
+fn parse_int_too_many_args() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseInt(\"100\", 10, 10)"), "100");
+}
+
+#[test]
+fn parse_float_simple() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(\"6.5\")"), "6.5");
+}
+
+#[test]
+fn parse_float_int() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(10)"), "10");
+}
+
+#[test]
+fn parse_float_int_str() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(\"8\")"), "8");
+}
+
+#[test]
+fn parse_float_already_float() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(17.5)"), "17.5");
+}
+
+#[test]
+fn parse_float_negative() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(\"-99.7\")"), "-99.7");
+}
+
+#[test]
+fn parse_float_malformed_str() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(\"hello\")"), "NaN");
+}
+
+#[test]
+fn parse_float_undefined() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(undefined)"), "NaN");
+}
+
+/// No arguments to parseFloat is treated the same as passing undefined as the first argument.
+#[test]
+fn parse_float_no_args() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat()"), "NaN");
+}
+
+/// Shows that the parseFloat function ignores extra arguments.
+#[test]
+fn parse_float_too_many_args() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    assert_eq!(&forward(&mut engine, "parseFloat(\"100.5\", 10)"), "100.5");
+}