diff --git a/src/humanize/number.py b/src/humanize/number.py
index 52a5356a..99d9f817 100644
--- a/src/humanize/number.py
+++ b/src/humanize/number.py
@@ -196,6 +196,12 @@ def intcomma(value: NumberOrString, ndigits: int | None = None) -> str:
 
     if ndigits is not None:
         result = f"{value:,.{ndigits}f}"
+    elif isinstance(value, float) and "e" in str(value):
+        from decimal import Decimal
+
+        result = f"{Decimal(str(value)):,f}"
+        if "." not in result:
+            result += ".0"
     else:
         result = f"{value:,}"
     if thousands_sep != "," or decimal_sep != ".":
diff --git a/tests/test_i18n.py b/tests/test_i18n.py
index 20db617b..aeaa2e85 100644
--- a/tests/test_i18n.py
+++ b/tests/test_i18n.py
@@ -115,6 +115,7 @@ def test_intcomma() -> None:
         assert humanize.intcomma("1234567,89") == "1.234.567,89"
         assert humanize.intcomma("1.234.567,89") == "1.234.567,89"
         assert humanize.intcomma("1.234.567,8") == "1.234.567,8"
+        assert humanize.intcomma(1.5e20) == "150.000.000.000.000.000.000,0"
 
         humanize.i18n.activate("fr_FR")
         assert humanize.intcomma(number) == "10 000 000"
diff --git a/tests/test_number.py b/tests/test_number.py
index 5fb12fa6..f78d1bd2 100644
--- a/tests/test_number.py
+++ b/tests/test_number.py
@@ -70,6 +70,13 @@ def test_ordinal(test_input: str, expected: str) -> None:
         ([1234.5454545, 2], "1,234.55"),
         ([1234.5454545, 3], "1,234.545"),
         ([1234.5454545, 10], "1,234.5454545000"),
+        ([1e15], "1,000,000,000,000,000.0"),
+        ([1e16], "10,000,000,000,000,000.0"),
+        ([-1e16], "-10,000,000,000,000,000.0"),
+        ([1.5e20], "150,000,000,000,000,000,000.0"),
+        ([1.2345e16], "12,345,000,000,000,000.0"),
+        ([1e-5], "0.00001"),
+        (["1.5e20"], "150,000,000,000,000,000,000.0"),
         ([math.nan], "NaN"),
         ([math.inf], "+Inf"),
         ([-math.inf], "-Inf"),