An election to the 56th Parliament of the United Kingdom for the constituency area of St Helens South and Whiston, held as part of the general election on 7 May 2015.
Labour hold by Marie Rimmer with a majority of 21,243 - 43.9% - on a turnout of 62.3%.
Candidates
| Name | Party | Vote | Vote share | Vote change |
| RIMMER, Marie | Lab | 28,950 | 59.8% | 6.9% |
| KEEGAN, Gillian | Con | 7,707 | 15.9% | -1.9% |
| BEIRNE, John | UKIP | 6,766 | 14.0% | 11.3% |
| SPENCER, Brian | LD | 2,737 | 5.7% | -16.6% |
| CHAN, James | Green | 2,237 | 4.6% | - |
Under section 13(b) of the Representation of the People Act 1985, a candidate gaining 5% or less of the vote share will forfeit their deposit.
An electorate of 77,720, having a valid vote count of 48,397 and an invalid vote count of 171.
Result declared at 03:50 on 8 May 2015.