diff --git a/stdnum/fr/rcs.py b/stdnum/fr/rcs.py
new file mode 100644
index 00000000..4debb98f
--- /dev/null
+++ b/stdnum/fr/rcs.py
@@ -0,0 +1,122 @@
+# rcs.py - functions for handling French NIR numbers
+# coding: utf-8
+#
+# Copyright (C) 2025
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301 USA
+
+"""RCS (French registration number for commercial companies).
+
+The RCS number (Registre du commerce et des sociétés) is given by INSEE to a company with commercial activity
+when created. It is required for most of administrative procedures.
+
+The number consists of "RCS" letters followed by name of the city where the company was registered
+followed by letter A for a retailer or B for society
+followed by the SIREN number
+
+More information:
+
+* https://entreprendre.service-public.fr/vosdroits/F31190
+
+>>> validate('RCS Nancy B 323 159 715')
+'RCS Nancy B 323 159 715'
+>>> validate('RCS Nancy B 323159715')
+'RCS Nancy B 323 159 715'
+>>> validate('RCS Nancy B323 159715')
+'RCS Nancy B 323 159 715'
+>>> validate('RCS Nancy B 323 159 716')  # invalid check digit
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('RCSNancy B 323 159 716')  # invalid format
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> validate('RCS NancyB 323 159 716')  # invalid format
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> format('RCS Nancy B323159715')
+'RCS Nancy B 323 159 715'
+>>> format('bad')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> to_siren("RCS Nancy B 323159 715")
+'323159 715'
+"""
+
+from __future__ import annotations
+
+import re
+
+from stdnum.exceptions import *
+from stdnum.fr import siren
+from stdnum.util import clean, isdigits
+
+
+RCS_VALIDATION_REGEX = (
+    r'^ *(?P<tag>RCS|rcs) +(?P<city>.*?) +(?P<letter>[AB]) *(?P<siren>(?:\d *){9})\b *$'
+)
+
+
+def validate(number: str) -> str:
+    """Validate number is a valid french RCS number."""
+    match = re.match(RCS_VALIDATION_REGEX, clean(number))
+    if not match:
+        raise InvalidFormat()
+    siren_number = siren.validate(match.group('siren'))
+    siren_number = siren.format(siren_number)
+
+    return format(number)
+
+
+def is_valid(number: str) -> bool:
+    """Check if the number provided is valid."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number: str) -> str:
+    """Reformat the number to the standard presentation format."""
+    match = re.match(RCS_VALIDATION_REGEX, clean(number))
+    if not match:
+        raise InvalidFormat()
+    return ' '.join(
+        (
+            'RCS',
+            match.group('city'),
+            match.group('letter'),
+            siren.format(match.group('siren')),
+        ),
+    )
+
+
+def to_siren(number: str) -> str:
+    """Extract SIREN number from the RCS number.
+
+    The SIREN number is the 9 last digits of the RCS number.
+    """
+    _siren: list[str] = []
+    digit_count = 0
+    for char in reversed(number):
+        if digit_count < 9:
+            _siren.insert(0, char)
+            if isdigits(char):
+                digit_count += 1
+    return ''.join(_siren)
diff --git a/stdnum/fr/siren.py b/stdnum/fr/siren.py
index e3607475..63d7732b 100644
--- a/stdnum/fr/siren.py
+++ b/stdnum/fr/siren.py
@@ -83,3 +83,9 @@ def to_tva(number: str) -> str:
         int(compact(number) + '12') % 97,
         ' ' if ' ' in number else '',
         number)
+
+
+def format(number: str, separator: str = ' ') -> str:
+    """Reformat the number to the standard presentation format."""
+    number = compact(number)
+    return separator.join((number[0:3], number[3:6], number[6:9]))