Joseph Matthäus Aigner (18 January 1818, Vienna – 19 February 1886, Vienna) was an Austrian portrait painter, who studied under Friedrich von Amerling and Carl Rahl. He painted portraits of Franz Joseph I of Austria and his wife Elizabeth, Franz Grillparzer, Friedrich Halm, Nikolaus Lenau, and Maximilian I of Mexico.
In 1847 he married actress Fanny Matras (1828–1878).
As commander of the Academic Legion during the 1848 revolutions in Vienna, Aigner was court-martialed for high treason and condemned to death. However, Alfred I, Prince of Windisch-Grätz pardoned him.
According to Ripley’s Believe It or Not!, a Capuchin monk, whose name Aigner never knew, saved his life three times, when he attempted to hang himself at ages 18 and 22 and when he was sentenced to death. Aigner successfully committed suicide with a pistol in Vienna in 1886, and the same monk presided over his funeral.