The Preston by-election, 1929 was a parliamentary by-election held in England for the House of Commons constituency of Preston on 31 July 1929. The seat had become vacant when the Liberal Member of Parliament William Jowitt had resigned his seat after changing his party allegiance. Jowitt held the seat with an increased majority. The Liberals did not put forward a candidate, being demoralised following Jowitt's defection, and also lacking funds to fight an election. They did not become a force at parliamentary level in Preston again.