The general election took place in 646 constituencies across the United Kingdom, under the first-past-the-post system, for seats in the House of Commons. All but one constituency polled on 5 May; the South Staffordshire vote was postponed and took place on 23 June due to the death of a candidate. For details by constituency, see 2005 general election results.

Local elections in parts of England and in Northern Ireland were held on the same day. The polls were open for 15 hours, from 07:00 to 22:00 BST (UTC+1). The election came just over three weeks after the dissolution of Parliament on 11 April by Queen Elizabeth II, at the request of the Prime Minister, Tony Blair.