diff --git a/README.md b/README.md
index 9682dc0..9dc5326 100644
--- a/README.md
+++ b/README.md
@@ -388,6 +388,7 @@ Symmetrically, the `EmptyContextWithBuiltinFunctions` has builtin functions enab
 | `math::sqrt`         | 1               | Numeric                       | Returns the square root of a number. Returns NaN for a negative number |
 | `math::cbrt`         | 1               | Numeric                       | Returns the cube root of a number |
 | `math::hypot`        | 2               | Numeric                       | Calculates the length of the hypotenuse of a right-angle triangle given legs of length given by the two arguments |
+| `math::abs`          | 1               | Numeric                       | Returns the absolute value of a number, returning an integer if the argument was an integer, and a float otherwise |
 | `str::regex_matches` | 2               | String, String                | Returns true if the first argument matches the regex in the second argument (Requires `regex_support` feature flag) |
 | `str::regex_replace` | 3               | String, String, String        | Returns the first argument with all matches of the regex in the second argument replaced by the third argument (Requires `regex_support` feature flag) |
 | `str::to_lowercase`  | 1               | String                        | Returns the lower-case version of the string |
diff --git a/src/function/builtin.rs b/src/function/builtin.rs
index 350a810..7105743 100644
--- a/src/function/builtin.rs
+++ b/src/function/builtin.rs
@@ -87,6 +87,12 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
         "math::is_finite" => float_is(FloatType::is_finite),
         "math::is_infinite" => float_is(FloatType::is_infinite),
         "math::is_normal" => float_is(FloatType::is_normal),
+        // Absolute
+        "math::abs" => Some(Function::new(|argument| match argument {
+            Value::Float(num) => Ok(Value::Float(num.abs())),
+            Value::Int(num) => Ok(Value::Int(num.abs())),
+            _ => Err(EvalexprError::expected_number(argument.clone())),
+        })),
         // Other
         "typeof" => Some(Function::new(move |argument| {
             Ok(match argument {
diff --git a/src/lib.rs b/src/lib.rs
index 673443b..cd28209 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -371,6 +371,7 @@
 //! | `math::sqrt`         | 1               | Numeric                       | Returns the square root of a number. Returns NaN for a negative number |
 //! | `math::cbrt`         | 1               | Numeric                       | Returns the cube root of a number |
 //! | `math::hypot`        | 2               | Numeric                       | Calculates the length of the hypotenuse of a right-angle triangle given legs of length given by the two arguments |
+//! | `math::abs`          | 1               | Numeric                       | Returns the absolute value of a number, returning an integer if the argument was an integer, and a float otherwise |
 //! | `str::regex_matches` | 2               | String, String                | Returns true if the first argument matches the regex in the second argument (Requires `regex_support` feature flag) |
 //! | `str::regex_replace` | 3               | String, String, String        | Returns the first argument with all matches of the regex in the second argument replaced by the third argument (Requires `regex_support` feature flag) |
 //! | `str::to_lowercase`  | 1               | String                        | Returns the lower-case version of the string |
diff --git a/tests/integration.rs b/tests/integration.rs
index c837fa2..0c97576 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -384,6 +384,11 @@ fn test_builtin_functions() {
     assert_eq!(eval("math::is_infinite(1.0/0.0)"), Ok(Value::Boolean(true)));
     assert_eq!(eval("math::is_normal(1.0/0.0)"), Ok(Value::Boolean(false)));
     assert_eq!(eval("math::is_normal(0)"), Ok(Value::Boolean(false)));
+    // Absolute
+    assert_eq!(eval("math::abs(15.4)"), Ok(Value::Float(15.4)));
+    assert_eq!(eval("math::abs(-15.4)"), Ok(Value::Float(15.4)));
+    assert_eq!(eval("math::abs(15)"), Ok(Value::Int(15)));
+    assert_eq!(eval("math::abs(-15)"), Ok(Value::Int(15)));
     // Other
     assert_eq!(eval("typeof(4.0, 3)"), Ok(Value::String("tuple".into())));
     assert_eq!(eval("typeof(4.0)"), Ok(Value::String("float".into())));