diff --git a/stdnum/se/bankgiro.py b/stdnum/se/bankgiro.py
new file mode 100644
index 00000000..5703520d
--- /dev/null
+++ b/stdnum/se/bankgiro.py
@@ -0,0 +1,88 @@
+# bankgiro.py - functions for handling Swedish Bankgiro numbers
+# coding: utf-8
+#
+# Copyright (C) 2026 Gracestack (Kim Cedendahl)
+#
+# 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, see <https://www.gnu.org/licenses/>.
+
+"""Bankgiro (Swedish bank giro number).
+
+The Bankgiro number is used in Sweden to identify bank giro accounts
+for invoice payments and other bank transfers. The number consists of
+7 or 8 digits and includes a check digit calculated using the Luhn
+(mod-10) algorithm, which is the same as used by the related PlusGiro
+numbers.
+
+Bankgiro numbers are commonly formatted as NNN-NNNN (7 digits) or
+NNNN-NNNN (8 digits) with a hyphen separating the groups.
+
+More information:
+
+* https://www.bankgirot.se/en/
+
+>>> validate('9000001')
+'9000001'
+>>> validate('9000002')  # invalid check digit
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('123456789')  # too long
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> format('9000001')
+'900-0001'
+>>> format('50501501')
+'5050-1501'
+"""
+
+from __future__ import annotations
+
+from stdnum import luhn
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+
+def compact(number: str) -> str:
+    """Convert the number to the minimal representation. This strips the
+    number of any valid separators and removes surrounding whitespace."""
+    return clean(number, ' -.').strip()
+
+
+def validate(number: str) -> str:
+    """Check if the number is a valid Bankgiro number. This checks
+    the length, formatting and check digit."""
+    number = compact(number)
+    if not isdigits(number):
+        raise InvalidFormat()
+    if len(number) not in (7, 8):
+        raise InvalidLength()
+    return luhn.validate(number)
+
+
+def is_valid(number: str) -> bool:
+    """Check if the number is a valid Bankgiro number."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number: str) -> str:
+    """Reformat the number to the standard presentation format."""
+    number = compact(number)
+    if len(number) == 7:
+        return number[:3] + '-' + number[3:]
+    else:
+        return number[:4] + '-' + number[4:]
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diff --git a/tests/test_se_bankgiro.doctest b/tests/test_se_bankgiro.doctest
new file mode 100644
index 00000000..d22a2eda
--- /dev/null
+++ b/tests/test_se_bankgiro.doctest
@@ -0,0 +1,100 @@
+test_se_bankgiro.doctest - more detailed doctests for stdnum.se.bankgiro module
+
+Copyright (C) 2026 Gracestack (Kim Cedendahl)
+
+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, see <https://www.gnu.org/licenses/>.
+
+
+This file contains more detailed doctests for the stdnum.se.bankgiro
+module. It tries to cover more corner cases and detailed functionality.
+
+>>> from stdnum.se import bankgiro
+
+
+Test valid 7-digit numbers.
+
+>>> bankgiro.validate('9000001')
+'9000001'
+>>> bankgiro.validate('900-0001')
+'9000001'
+
+
+Test valid 8-digit numbers.
+
+>>> bankgiro.validate('50501501')
+'50501501'
+>>> bankgiro.validate('5050-1501')
+'50501501'
+
+
+Test formatting variants.
+
+>>> bankgiro.format('9000001')
+'900-0001'
+>>> bankgiro.format('50501501')
+'5050-1501'
+>>> bankgiro.format('900-0001')
+'900-0001'
+>>> bankgiro.format('5050-1501')
+'5050-1501'
+
+
+Test compact.
+
+>>> bankgiro.compact('900-0001')
+'9000001'
+>>> bankgiro.compact('  5050 1501  ')
+'50501501'
+
+
+Test invalid numbers (wrong check digit).
+
+>>> bankgiro.validate('9000002')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+
+
+Test invalid length.
+
+>>> bankgiro.validate('12345')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> bankgiro.validate('123456789')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+
+
+Test invalid format (non-numeric).
+
+>>> bankgiro.validate('abcdefg')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> bankgiro.validate('')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+
+
+Test is_valid convenience function.
+
+>>> bankgiro.is_valid('9000001')
+True
+>>> bankgiro.is_valid('9000002')
+False
+>>> bankgiro.is_valid('')
+False
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