Brecon by-election or similar terms may refer to:
1854 Brecon by-election 1858 Breconshire by-election 1875 Breconshire by-election February 1866 Brecon by-election October 1866 Brecon by-election 1869 Brecon by-election 1870 Brecon by-election 1939 Brecon and Radnorshire by-election 1985 Brecon and Radnor by-election 2019 Brecon and Radnorshire by-election