The Leicester South by-election was held to elect a Member of Parliament (MP) of the United Kingdom for the Leicester South constituency on 5 May 2011. It was prompted by the resignation of Sir Peter Soulsby of the Labour Party, who stood down from Parliament to contest the election for Mayor of Leicester. Soulsby was appointed Crown Steward and Bailiff of the Manor of Northstead on 1 April 2011, and the writ for a new election was issued on 5 April. The election was won by Labour Party candidate Jon Ashworth.