West Down was a United Kingdom parliamentary constituency in Ireland. It returned one Member of Parliament (MP) to the House of Commons of the United Kingdom from 1885 to 1922, on the electoral system of first past the post.
From 1801 to 1885, County Down returned two MPs to the House of Commons of the United Kingdom sitting at the Palace of Westminster, with separate representation for the parliamentary boroughs of Downpatrick and Newry. Under the Redistribution of Seats Act 1885, Downpatrick ceased to exist as a parliamentary borough and the parliamentary county was divided into four divisions: North Down, East Down, West Down, and South Down.
Under the Redistribution of Seats (Ireland) Act 1918, Newry ceased to exist as a parliamentary borough, and the parliamentary county gained the additional division of Mid Down. Sinn Féin contested the 1918 general election on an abstentionist platform that instead of taking up any seats at Westminster, they would establish a revolutionary assembly in Dublin. All MPs elected to Irish seats were invited to participate in the First Dáil convened in January 1919, but no members outside of Sinn Féin did so.
The Government of Ireland Act 1920 established the Parliament of Northern Ireland, which came into operation in 1921. The representation of Northern Ireland in the Parliament of the United Kingdom was reduced from 30 MPs to 13 MPs, taking effect at the 1922 United Kingdom general election. At Westminster, the five divisions of County Down were replaced by a two-member county constituency of Down. An eight-seat constituency of Down was created for the House of Commons of Northern Ireland, which formed the basis in republican theory for representation in the Second Dáil.
Hill was re-appointed Comptroller of the Household, requiring a by-election.