Joseph Effner (February 4, 1687 (baptized) – February 23, 1745) was a German architect and decorator.
Effner was born in Dachau as a son of the court gardener Christian Öffner. Effner accompanied the elector of Bavaria Max Emanuel to Bruxelles. In 1706 Effner was retrained by Gabriel Germain Boffrand in Paris. Here he changed his family name to "Effner". In 1717 Effner was sent by the elector to Italy for a study trip. From 1715 to 1726 Effner was then court architect to the elector. With the accession to power of Charles Albert in 1726 Effner was replaced by his pupil François de Cuvilliés and then worked in the administration. He died in Munich.