diff --git a/src/algorithms/__init__.py b/src/algorithms/__init__.py
new file mode 100644
index 0000000..92f33b3
--- /dev/null
+++ b/src/algorithms/__init__.py
@@ -0,0 +1 @@
+# algorithms package
diff --git a/src/algorithms/find_max.py b/src/algorithms/find_max.py
new file mode 100644
index 0000000..e71fd53
--- /dev/null
+++ b/src/algorithms/find_max.py
@@ -0,0 +1,14 @@
+"""find_max — 从数字列表中查找最大值"""
+
+from __future__ import annotations
+
+
+def find_max(nums: list[int | float]) -> int | float | None:
+    """返回列表中的最大值，空列表返回 None。"""
+    if not nums:
+        return None
+    result = nums[0]
+    for num in nums[1:]:
+        if num > result:
+            result = num
+    return result
diff --git a/tests/test_find_max.py b/tests/test_find_max.py
new file mode 100644
index 0000000..1bbdb1b
--- /dev/null
+++ b/tests/test_find_max.py
@@ -0,0 +1,28 @@
+"""find_max 单元测试"""
+
+import pytest
+
+from src.algorithms.find_max import find_max
+
+
+class TestFindMax:
+    def test_normal_list(self):
+        assert find_max([3, 1, 4, 1, 5, 9, 2, 6]) == 9
+
+    def test_empty_list(self):
+        assert find_max([]) is None
+
+    def test_single_element(self):
+        assert find_max([42]) == 42
+
+    def test_negative_numbers(self):
+        assert find_max([-5, -1, -10, -3]) == -1
+
+    def test_floats(self):
+        assert find_max([1.5, 2.7, 0.3, 3.14]) == 3.14
+
+    def test_mixed_int_float(self):
+        assert find_max([1, 2.5, 3, 0.1]) == 3
+
+    def test_duplicate_max(self):
+        assert find_max([7, 7, 7]) == 7