The Brecon and Radnor by-election, 1985 was a parliamentary by-election held on 4 July 1985 for the British House of Commons constituency of Brecon and Radnor.
The seat had become vacant on 9 May 1985, when the constituency's Conservative Member of Parliament (MP), Tom Ellis Hooson, had died at the age of 52. He was a cousin of Emlyn Hooson, the former Liberal Party MP for Montgomery.
Tom Hooson had been Brecon and Radnor's MP since the 1979 general election, when he gained the seat from the Labour Party.
Seven candidates were nominated.
1. Richard Arthur Lloyd Livsey was the candidate of the Liberal Party and represented the SDP-Liberal Alliance. He was a former senior lecturer in farm management, born in 1935, who had become a smallholder. He had contested the seat in the 1983 general election.
2. (Frederick) Richard Willey, born 1945, was the Labour candidate. He was the son of veteran Labour MP Fred Willey and a member of Radnor District Council. He was a freelance educational researcher and writer.
3. Christopher John Butler, born 1950, represented the Conservative Party. He was a special adviser to the Secretary of State for Wales and had previously worked at the Conservative Research Department in Wales and the Political Office in 10 Downing Street.