A by-election for the Tasmanian House of Assembly was held in the Division of Denison in the Australian state of Tasmania on Saturday 16 February 1980.

[1] In previous elections, candidates were listed in alphabetical order by surname.

By-elections are not usually held in the Tasmanian House of Assembly because casual vacancies are filled by a countback of votes, a system that has been in place since 1917.

The election resulted in two previously elected members losing their seats: John Green from the Labor Party and Bob Baker from the Liberal Party.

Elected in their place were Norm Sanders from the Democrats and Liberal Gabriel Haros.