diff --git a/src/humanize/number.py b/src/humanize/number.py
index 52a5356a..b95e2420 100644
--- a/src/humanize/number.py
+++ b/src/humanize/number.py
@@ -173,9 +173,16 @@ def intcomma(value: NumberOrString, ndigits: int | None = None) -> str:
 
     Returns:
         str: String containing commas every three digits.
+
+    Raises:
+        ValueError: If `ndigits` is negative.
     """
     import math
 
+    if ndigits is not None and ndigits < 0:
+        msg = f"ndigits must be >= 0, got {ndigits}"
+        raise ValueError(msg)
+
     thousands_sep = thousands_separator()
     decimal_sep = decimal_separator()
     try:
diff --git a/tests/test_number.py b/tests/test_number.py
index 5fb12fa6..41a6bcb8 100644
--- a/tests/test_number.py
+++ b/tests/test_number.py
@@ -83,6 +83,12 @@ def test_intcomma(
     assert humanize.intcomma(*test_args) == expected
 
 
+@pytest.mark.parametrize("value", [12345.111, 12345, "12345.111", None])
+def test_intcomma_negative_ndigits(value: float | str | None) -> None:
+    with pytest.raises(ValueError, match="ndigits must be >= 0"):
+        humanize.intcomma(value, -1)
+
+
 @pytest.mark.parametrize("sign", [1, -1])
 def test_intcomma_large_integer(sign: int) -> None:
     value = sign * (10**400 + 123)