An election to the 56th Parliament of the United Kingdom for the constituency area of Cardiff South and Penarth, held as part of the general election on 7 May 2015.
Labour hold by Stephen Doughty with a majority of 7,453 - 16.0% - on a turnout of 61.4%.
Candidates
| Name | Party | Vote | Vote share | Vote change |
| DOUGHTY, Stephen | Lab / Co-op | 19,966 | 42.8% | 3.9% |
| WARMAN, Emma | Con | 12,513 | 26.8% | -1.5% |
| REES-EVANS, John | UKIP | 6,423 | 13.8% | 11.2% |
| FODAY, Ben | PC | 3,443 | 7.4% | 3.2% |
| HOWELLS, Nigel | LD | 2,318 | 5.0% | -17.3% |
| SLAUGHTER, Anthony | Green | 1,746 | 3.7% | 2.5% |
| SAUNDERS, Ross | TUSC | 258 | 0.6% | - |
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 76,006, having a valid vote count of 46,667 and an invalid vote count of 121.
Result declared at 03:45 on 8 May 2015.