South West Lancashire was a county constituency of the House of Commons of the Parliament of the United Kingdom.
The constituency was abolished by the Redistribution of Seats Act 1885, being divided into eight single member divisions of Bootle, Ince, Leigh, Newton, Ormskirk, St Helens, Southport and Widnes.
This constituency comprised the Lancashire hundred of West Derby except for the boroughs of Liverpool, Warrington and Wigan.
Cross sought re-election after being appointed as Home Secretary.
Cross was appointed Home Secretary, requiring a by-election.