Armed Forces is the third studio album by the English singer-songwriter Elvis Costello, released on 5 January 1979 in the United Kingdom through Radar Records. It was his second album with the Attractions—keyboardist Steve Nieve, bassist Bruce Thomas and drummer Pete Thomas (no relation)—and the first to officially credit them on the cover. The album was recorded in six weeks from August to September 1978 in London under the working title Emotional Fascism. Produced by Nick Lowe and engineered by Roger Béchirian, the sessions saw Costello exert more control over production compared to This Year's Model, while Nieve contributed more to song arrangements.

For Armed Forces, Costello sought a more commercial sound than the punk rock style employed on his two previous records, resulting in a more pop-oriented production reflecting the new wave era. The overtly political lyrics concern the effect of politics on human relationships. The UK release featured an elaborate fold-out LP packaging, with a cover depicting a herd of elephants; it was simplified for the US release through Columbia Records, featuring an alternate drip-cover.

Supported by the successful UK singles "Oliver's Army" and "Accidents Will Happen", Armed Forces reached number two in the UK, becoming Costello's biggest commercial success up to that point. The American version, released in February 1979, omitted "Sunday's Best" and replaced it with Costello's version of Lowe's "(What's So Funny 'Bout) Peace, Love, and Understanding". The album received positive reviews from music critics and appeared on several lists of the year's best albums. Costello and the Attractions supported the album on the Armed Funk tour in America.

In later decades, Armed Forces has continued to receive positive reviews, with many highlighting the production. Others noted that it contained musical styles Costello would utilise for later records. It is considered one of Costello's best works and has appeared on various best-of lists. The album has been reissued multiple times, including in 2020 as a super deluxe edition, which was positively received.