St Helens South was a borough constituency represented in the House of Commons of the Parliament of the United Kingdom.

The Borough of St Helens wards of Eccleston, Grange Park, Marshalls Cross, Parr and Hardshaw, Queen's Park, Rainhill, Sutton and Bold, Thatto Heath, and West Sutton.

Following recommendations made by the Boundary Commission for England, St Helens South was replaced with a new St Helens South and Whiston constituency, which includes three wards from Knowsley borough.

The constituency was formed in 1983, and was represented by Labour's Gerry Bermingham from then until he stood down in 2001.

Woodward was deemed unlikely to retain his Witney constituency in Oxfordshire as a Labour candidate (it was subsequently won by David Cameron, former Leader of the Conservatives and Prime Minister of the United Kingdom), and was instead selected for this safe seat.