diff --git a/newsfragments/+d4a9206f.bugfix.rst b/newsfragments/+d4a9206f.bugfix.rst
new file mode 100644
index 0000000000..b066641029
--- /dev/null
+++ b/newsfragments/+d4a9206f.bugfix.rst
@@ -0,0 +1 @@
+Retain valid names with underscores in egg_info.
\ No newline at end of file
diff --git a/setuptools/_normalization.py b/setuptools/_normalization.py
index eee4fb7746..aa9274f093 100644
--- a/setuptools/_normalization.py
+++ b/setuptools/_normalization.py
@@ -12,7 +12,7 @@
 
 # https://packaging.python.org/en/latest/specifications/core-metadata/#name
 _VALID_NAME = re.compile(r"^([A-Z0-9]|[A-Z0-9][A-Z0-9._-]*[A-Z0-9])$", re.I)
-_UNSAFE_NAME_CHARS = re.compile(r"[^A-Z0-9.]+", re.I)
+_UNSAFE_NAME_CHARS = re.compile(r"[^A-Z0-9._-]+", re.I)
 _NON_ALPHANUMERIC = re.compile(r"[^A-Z0-9]+", re.I)
 _PEP440_FALLBACK = re.compile(r"^v?(?P<safe>(?:[0-9]+!)?[0-9]+(?:\.[0-9]+)*)", re.I)
 
@@ -35,6 +35,8 @@ def safe_name(component: str) -> str:
     'hello-world'
     >>> safe_name("hello?world")
     'hello-world'
+    >>> safe_name("hello_world")
+    'hello_world'
     """
     # See pkg_resources.safe_name
     return _UNSAFE_NAME_CHARS.sub("-", component)