The flag of the Western European Union (WEU) was dark blue with a semicircle of ten yellow five pointed stars, broken at the top, with the organisation's initials in the centre.

The flag is dark blue with a semicircle of ten yellow five pointed stars, broken at the top, with the white letters WEU horizontally across the centre and UEO vertically across the centre sharing the letter E with the former set of initials.

This design replaced the flag of the Western Union, the organisation that was transformed into the WEU upon the entry into force of the Modified Brussels Treaty.

The flag was rarely used, with the WEU being largely dormant before it was succeeded by the European Union's (EU) military activities.

It was once flown on board an operational United States Navy warship, USS John Rodgers, when it was used as the flagship of an Italian general (with a WEU crew) commanding WEU relief operations in Bosnia and Herzegovina.