diff --git a/README b/README
index c0953cf9..15a3e7c6 100644
--- a/README
+++ b/README
@@ -170,6 +170,7 @@ Currently this package supports the following formats:
  * PESEL (Polish national identification number)
  * REGON (Rejestr Gospodarki Narodowej, Polish register of economic units)
  * NIF (Número de identificação fiscal, Portuguese VAT number)
+ * CC (Número de Cartão de Cidadão, Portuguese Identity number)
  * RUC number (Registro Único de Contribuyentes, Paraguay tax number)
  * CF (Cod de înregistrare în scopuri de TVA, Romanian VAT number)
  * CNP (Cod Numeric Personal, Romanian Numerical Personal Code)
diff --git a/docs/index.rst b/docs/index.rst
index 03e1cfc7..9cac2d71 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -267,6 +267,7 @@ Available formats
    pl.nip
    pl.pesel
    pl.regon
+   pt.cc
    pt.nif
    py.ruc
    ro.cf
diff --git a/docs/stdnum.pt.cc.rst b/docs/stdnum.pt.cc.rst
new file mode 100644
index 00000000..52d23bae
--- /dev/null
+++ b/docs/stdnum.pt.cc.rst
@@ -0,0 +1,5 @@
+stdnum.pt.cc
+=============
+
+.. automodule:: stdnum.pt.cc
+   :members:
diff --git a/stdnum/pt/cc.py b/stdnum/pt/cc.py
new file mode 100644
index 00000000..a8e4b1e7
--- /dev/null
+++ b/stdnum/pt/cc.py
@@ -0,0 +1,110 @@
+# cc.py - functions for handling Portuguese Identity numbers
+# coding: utf-8
+#
+# Copyright (C) 2021 David Vaz
+#
+# 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
+
+"""CC (Número de Cartão de Cidadão, Portuguese Identity number).
+
+The Portuguese Identity Number is alfanumeric with the following format:
+
+DDDDDDDD C AAT
+
+with:
+D - Civil Identity Number [0-9]
+C - Civil Identity Number Check Digit [0-9]
+A - Version [A-Z0-9]
+T - Identity Number Check Digit [0-9]
+
+Full definition in Portuguese can be found here:
+https://www.autenticacao.gov.pt/documents/20126/115760/Valida%C3%A7%C3%A3o+de+N%C3%BAmero+de+Documento+do+Cart%C3%A3o+de+Cidad%C3%A3o.pdf
+
+>>> validate('00000000 0 ZZ4')
+'000000000ZZ4'
+>>> validate('00000000 A ZZ4')  # invalid format
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> validate('00000000 0 ZZ3')  # invalid check digits
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+"""
+import re
+
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+_cc_re = re.compile(r'^\d*[A-Z0-9]{2}\d$')
+
+
+def compact(number):
+    """Convert the number to the minimal representation. This strips the
+    number of any valid separators and removes surrounding whitespace."""
+    number = clean(number, ' ').upper().strip()
+    return number
+
+
+def _alphabet_convert(char):
+    """
+    alphabet table conversion:
+    0: 0, .. 9: 9
+    A:10, B: 11 .. Z:35
+    """
+    if isdigits(char):
+        return ord(char) - ord('0')
+    return ord(char) - ord('A') + 10
+
+
+def calc_check_digit(number):
+    """Calculate the check digits for the number."""
+    value_sum = 0
+    for i in range(len(number) - 1, -1, -1):
+        value = _alphabet_convert(number[i])
+        if i % 2 == 0:
+            value *= 2
+            if value > 9:
+                value -= 9
+        value_sum += value
+    return str(10 - value_sum % 10)
+
+
+def validate(number):
+    """checks if the number is a valid cartao de cidadao number"""
+    number = compact(number)
+
+    if not _cc_re.match(number):
+        raise InvalidFormat()
+
+    if calc_check_digit(number[:-1]) != number[-1]:
+        raise InvalidChecksum()
+
+    return number
+
+
+def is_valid(number):
+    """Check if the number is a valid cartao de cidadao number"""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number):
+    """Reformat the number to the standard presentation format."""
+    number = compact(number)
+    return ' '.join([number[:-4], number[-4], number[-3:]])