1990 Knowsley South by-election

The 1990 Knowsley South by-election was a by-election held on 27 September 1990 for the British House of Commons constituency of Knowsley South in Merseyside.

The by-election was caused by the death of the constituency's Labour Party Member of Parliament (MP) Sean Hughes on 25 June.

The result was a Labour hold, with Edward O'Hara winning a majority of over 11,000 votes.