Blaby was a county constituency represented in the House of Commons of the Parliament of the United Kingdom, which existed from 1974 until 2010. It elected one Member of Parliament (MP) by the first past the post system of election. It was a safe seat for the Conservative Party, being held by Conservative MPs throughout its existence.

Blaby constituency was created in 1974 from parts of the Harborough seat. It is named after the village of Blaby in south west Leicestershire. A safe Conservative seat consisting mostly of middle-class commuter towns and villages for the neighbouring city of Leicester, it was held for many years by the former Chancellor of the Exchequer Nigel Lawson. Lawson was succeeded in 1992 by Andrew Robathan, who held the seat until its abolition.

Following its review of parliamentary representation in Leicestershire, the Boundary Commission for England renamed the Blaby constituency as South Leicestershire, with minor alterations to its boundaries, in time for the 2010 election.

1974–1983: The Rural Districts of Blaby and Lutterworth.

1983–1997: The District of Blaby, and the District of Harborough wards of Broughton, Dunton, Gilmorton, Kilworth, Lutterworth Linden, Lutterworth St Mary's, Lutterworth Sherrier, Lutterworth Wycliffe, Peatling, and Ullesthorpe.

1997–2010: The District of Blaby wards of Cosby, Countesthorpe, Croft Hill, Enderby, Flamville, Fosse, Glen Parva, Millfield, Narborough, Normanton, Northfield, Ravenhurst, St John's, Stanton, Whetstone, Winchester, and Winstanley, and the District of Harborough wards of Broughton, Dunton, Gilmorton, Kilworth, Lutterworth Linden, Lutterworth St Mary's, Lutterworth Sherrier, Lutterworth Wycliffe, Peatling, and Ullesthorpe.

• List of parliamentary constituencies in Leicestershire and Rutland