The Westland affair was a political crisis for the Conservative government of Margaret Thatcher in 1986.

The argument was a result of differences of opinion within the government as to the future of the UK helicopter industry. The struggling Westland company, Britain's last helicopter manufacturer, was to be the subject of a rescue bid. While the Defence Secretary Michael Heseltine favoured a European solution, integrating Westland and BAe with Italian (Agusta) and French companies, the Prime Minister and the Trade and Industry Secretary Leon Brittan wanted to see Westland merge with Sikorsky, an American company.

In January 1986 during a Cabinet meeting Heseltine walked out of Downing Street and announced his resignation to the assembled media. He blamed Thatcher's intransigence — saying his views were ignored.

The crisis refused to die down and two weeks later Leon Brittan was force to resign when it emerged that he leaked a government law officer's memo which was critical of Heseltine.

This event would be seen later as the beginning of the end of Thatcher's premiership, Heseltine challenged the Prime Minister for leadership of the Conservative Party in 1990 — which led to her downfall.

Several ironies are present in subsequent events — Heseltine's wish to see a strong European competitor has emerged in the form of the Eurocopter group and Agusta would eventually merge with Westland in 2000 and then acquire GKN's stake in 2004.