The Western Union (WU) was a military alliance established between France, the United Kingdom and the three Benelux countries between 1948 and 1954. The flag of the Western Union, also referred to as the Western Union Standard, displays an unbroken chain of five rectangular links in the shape of an upside-down pentagon on a blue field, with a multicoloured border taken from the WU member states' flags.

The Western Union (WU), also referred to as the Brussels Treaty Organisation (BTO), was the European military alliance established between France, the United Kingdom (UK) and the three Benelux countries in September 1948 in order to implement the Treaty of Brussels signed in March the same year. Under this treaty the signatories, referred to as the five powers, agreed to collaborate in the defence field as well as in the political, economic and cultural fields.