diff --git a/compiler/builtins/src/std.rs b/compiler/builtins/src/std.rs
index 55ed8dc92f..7735290ce6 100644
--- a/compiler/builtins/src/std.rs
+++ b/compiler/builtins/src/std.rs
@@ -285,6 +285,12 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         SolvedType::Func(vec![int_type(), int_type()], Box::new(bool_type())),
     );
 
+    // abs : Int -> Int
+    add_type(
+        Symbol::INT_ABS,
+        SolvedType::Func(vec![int_type()], Box::new(int_type())),
+    );
+
     // highest : Int
     add_type(Symbol::INT_HIGHEST, int_type());
 
@@ -336,6 +342,12 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         SolvedType::Func(vec![float_type()], Box::new(int_type())),
     );
 
+    // abs : Float -> Float
+    add_type(
+        Symbol::FLOAT_ABS,
+        SolvedType::Func(vec![float_type()], Box::new(float_type())),
+    );
+
     // highest : Float
     add_type(Symbol::FLOAT_HIGHEST, float_type());
 
diff --git a/compiler/builtins/src/unique.rs b/compiler/builtins/src/unique.rs
index 92330d31b7..e87739bb0c 100644
--- a/compiler/builtins/src/unique.rs
+++ b/compiler/builtins/src/unique.rs
@@ -354,6 +354,12 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         unique_function(vec![int_type(UVAR1), int_type(UVAR2)], bool_type(UVAR3)),
     );
 
+    // abs :: Int -> Int
+    add_type(
+        Symbol::INT_ABS,
+        unique_function(vec![int_type(UVAR1)], int_type(UVAR2)),
+    );
+
     // highest : Int
     add_type(Symbol::INT_HIGHEST, int_type(UVAR1));
 
@@ -418,6 +424,12 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         unique_function(vec![float_type(UVAR1)], int_type(UVAR2)),
     );
 
+    // abs : Float -> Float
+    add_type(
+        Symbol::FLOAT_ABS,
+        unique_function(vec![float_type(UVAR1)], float_type(UVAR2)),
+    );
+
     // highest : Float
     add_type(Symbol::FLOAT_HIGHEST, float_type(UVAR1));
 
diff --git a/compiler/gen/src/llvm/build.rs b/compiler/gen/src/llvm/build.rs
index de5334c352..9adad722aa 100644
--- a/compiler/gen/src/llvm/build.rs
+++ b/compiler/gen/src/llvm/build.rs
@@ -80,10 +80,17 @@ fn add_intrinsics<'ctx>(ctx: &'ctx Context, module: &Module<'ctx>) {
         LLVM_LROUND_I64_F64,
         i64_type.fn_type(&[f64_type.into()], false),
     );
+
+    add_intrinsic(
+        module,
+        LLVM_FABS_F64,
+        f64_type.fn_type(&[f64_type.into()], false),
+    );
 }
 
 static LLVM_SQRT_F64: &str = "llvm.sqrt.f64";
 static LLVM_LROUND_I64_F64: &str = "llvm.lround.i64.f64";
+static LLVM_FABS_F64: &str = "llvm.fabs.f64";
 
 fn add_intrinsic<'ctx>(
     module: &Module<'ctx>,
@@ -1087,6 +1094,10 @@ fn call_with_args<'a, 'ctx, 'env>(
 
             BasicValueEnum::FloatValue(float_val)
         }
+        Symbol::NUM_ABS | Symbol::INT_ABS => {
+            todo!("implement intrinsic for int_abs")
+        },
+        Symbol::FLOAT_ABS => call_intrinsic(LLVM_FABS_F64, env, args),
         Symbol::INT_GTE | Symbol::NUM_GTE => {
             debug_assert!(args.len() == 2);
 
diff --git a/compiler/gen/tests/gen_builtins.rs b/compiler/gen/tests/gen_builtins.rs
index 1c166c110c..5030ed3505 100644
--- a/compiler/gen/tests/gen_builtins.rs
+++ b/compiler/gen/tests/gen_builtins.rs
@@ -37,6 +37,12 @@ mod gen_builtins {
         assert_evals_to!("Float.round 3.6", 4, i64);
     }
 
+    #[test]
+    fn f64_abs() {
+        assert_evals_to!("Float.abs -4.7", 4.7, f64);
+        assert_evals_to!("Float.abs 5.8", 5.8, f64);
+    }
+
     #[test]
     fn empty_list_literal() {
         assert_evals_to!("[]", &[], &'static [i64]);
diff --git a/compiler/module/src/symbol.rs b/compiler/module/src/symbol.rs
index bb2c11ff2d..4ea27186d4 100644
--- a/compiler/module/src/symbol.rs
+++ b/compiler/module/src/symbol.rs
@@ -609,6 +609,7 @@ define_builtins! {
         19 INT_NEQ_I64: "#neqi64"
         20 INT_NEQ_I1: "#neqi1"
         21 INT_NEQ_I8: "#neqi8"
+        22 INT_ABS: "abs"
     }
     3 FLOAT: "Float" => {
         0 FLOAT_FLOAT: "Float" imported // the Float.Float type alias
@@ -627,6 +628,7 @@ define_builtins! {
         13 FLOAT_LTE: "#lte"
         14 FLOAT_GT: "#gt"
         15 FLOAT_GTE: "#gte"
+        16 FLOAT_ABS: "abs"
     }
     4 BOOL: "Bool" => {
         0 BOOL_BOOL: "Bool" imported // the Bool.Bool type alias
diff --git a/compiler/solve/tests/test_uniq_solve.rs b/compiler/solve/tests/test_uniq_solve.rs
index 717c518b4d..01bae0722e 100644
--- a/compiler/solve/tests/test_uniq_solve.rs
+++ b/compiler/solve/tests/test_uniq_solve.rs
@@ -2097,8 +2097,8 @@ mod test_uniq_solve {
                     reverse
                 "#
             ),
-            "Attr * (Attr * (List (Attr (a | b) c)) -> Attr (* | a | b) (List (Attr b c)))",
-            // "Attr * (Attr * (List (Attr (a | b) c)) -> Attr (* | a | b) (List (Attr a c)))",
+            // "Attr * (Attr * (List (Attr (a | b) c)) -> Attr (* | a | b) (List (Attr b c)))",
+            "Attr * (Attr * (List (Attr (a | b) c)) -> Attr (* | a | b) (List (Attr a c)))",
         );
     }