diff --git a/compiler/builtins/docs/Num.roc b/compiler/builtins/docs/Num.roc
index df39d4849d..34fb2ca201 100644
--- a/compiler/builtins/docs/Num.roc
+++ b/compiler/builtins/docs/Num.roc
@@ -65,6 +65,7 @@ interface Num
             maxI128,
             maxInt,
             minFloat,
+            minI128,
             minInt,
             modInt,
             modFloat,
@@ -822,6 +823,25 @@ maxU32 : U32
 ## and zero is the lowest unsigned number. Unsigned numbers cannot be negative.
 minU32 : U32
 
+## The highest number that can be stored in an #I128 without overflowing its
+## available memory and crashing.
+##
+## For reference, this number is `170_141_183_460_469_231_731_687_303_715_884_105_727`,
+## which is over 2 million.
+##
+## Note that this is smaller than the positive version of #Int.minI128,
+## which means if you call #Num.abs on #Int.minI128, it will overflow and crash!
+maxI128 : I128
+
+## The min number that can be stored in an #I128 without underflowing its
+## available memory and crashing.
+##
+## For reference, this number is `-170_141_183_460_469_231_731_687_303_715_884_105_728`.
+##
+## Note that the positive version of this number is larger than #Int.maxI128,
+## which means if you call #Num.abs on #Int.minI128, it will overflow and crash!
+minI128 : I128
+
 ## The highest supported #F64 value you can have, which is approximately 1.8 × 10^308.
 ##
 ## If you go higher than this, your running Roc code will crash - so be careful not to!
diff --git a/compiler/builtins/src/std.rs b/compiler/builtins/src/std.rs
index db6d917a7c..d338d34959 100644
--- a/compiler/builtins/src/std.rs
+++ b/compiler/builtins/src/std.rs
@@ -397,6 +397,9 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         Box::new(bool_type()),
     );
 
+    // minI128 : I128
+    add_type!(Symbol::NUM_MIN_I128, i128_type());
+
     // maxI128 : I128
     add_type!(Symbol::NUM_MAX_I128, i128_type());
 
diff --git a/compiler/can/src/builtins.rs b/compiler/can/src/builtins.rs
index 04a1a1d9c8..696df17538 100644
--- a/compiler/can/src/builtins.rs
+++ b/compiler/can/src/builtins.rs
@@ -206,6 +206,7 @@ pub fn builtin_defs_map(symbol: Symbol, var_store: &mut VarStore) -> Option<Def>
         NUM_SHIFT_RIGHT => num_shift_right_by,
         NUM_SHIFT_RIGHT_ZERO_FILL => num_shift_right_zf_by,
         NUM_INT_CAST=> num_int_cast,
+        NUM_MIN_I128=> num_min_i128,
         NUM_MAX_I128=> num_max_i128,
         NUM_TO_STR => num_to_str,
         RESULT_MAP => result_map,
@@ -1237,6 +1238,35 @@ fn num_int_cast(symbol: Symbol, var_store: &mut VarStore) -> Def {
     lowlevel_1(symbol, LowLevel::NumIntCast, var_store)
 }
 
+/// Num.minI128: I128
+fn num_min_i128(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let int_var = var_store.fresh();
+    let int_precision_var = var_store.fresh();
+    // TODO: or `i128::MIN.into()` ?
+    let body = int(int_var, int_precision_var, i128::MIN);
+
+    let std = roc_builtins::std::types();
+    let solved = std.get(&symbol).unwrap();
+    let mut free_vars = roc_types::solved_types::FreeVars::default();
+    let signature = roc_types::solved_types::to_type(&solved.0, &mut free_vars, var_store);
+
+    let annotation = crate::def::Annotation {
+        signature,
+        introduced_variables: Default::default(),
+        region: Region::zero(),
+        aliases: Default::default(),
+    };
+
+    Def {
+        // TODO: or `None` ?
+        annotation: Some(annotation),
+        expr_var: int_var,
+        loc_expr: Loc::at_zero(body),
+        loc_pattern: Loc::at_zero(Pattern::Identifier(symbol)),
+        pattern_vars: SendMap::default(),
+    }
+}
+
 /// Num.maxI128: I128
 fn num_max_i128(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let int_var = var_store.fresh();
diff --git a/compiler/module/src/symbol.rs b/compiler/module/src/symbol.rs
index 237f72b199..f2e4c31059 100644
--- a/compiler/module/src/symbol.rs
+++ b/compiler/module/src/symbol.rs
@@ -995,6 +995,7 @@ define_builtins! {
         107 NUM_CAST_TO_NAT: "#castToNat"
         108 NUM_DIV_CEIL: "divCeil"
         109 NUM_TO_STR: "toStr"
+        110 NUM_MIN_I128: "minI128"
     }
     2 BOOL: "Bool" => {
         0 BOOL_BOOL: "Bool" imported // the Bool.Bool type alias
diff --git a/compiler/solve/tests/solve_expr.rs b/compiler/solve/tests/solve_expr.rs
index 7ada9982f1..2a4e285971 100644
--- a/compiler/solve/tests/solve_expr.rs
+++ b/compiler/solve/tests/solve_expr.rs
@@ -3341,6 +3341,18 @@ mod solve_expr {
         );
     }
 
+    #[test]
+    fn min_i128() {
+        infer_eq_without_problem(
+            indoc!(
+                r#"
+                Num.minI128
+                "#
+            ),
+            "I128",
+        );
+    }
+
     #[test]
     fn max_i128() {
         infer_eq_without_problem(
diff --git a/compiler/test_gen/src/gen_num.rs b/compiler/test_gen/src/gen_num.rs
index 3fc1227f70..88096f5b39 100644
--- a/compiler/test_gen/src/gen_num.rs
+++ b/compiler/test_gen/src/gen_num.rs
@@ -1829,6 +1829,20 @@ fn shift_right_zf_by() {
     assert_evals_to!("Num.shiftRightBy 3 0b0000_1100u8", 0b0000_0011, i64);
 }
 
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn min_i128() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+                Num.minI128
+                "#
+        ),
+        i128::MIN,
+        i128
+    );
+}
+
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 fn max_i128() {