Johann Baptist Joseph Maximilian Reger (19 March 1873 – 11 May 1916) was a German composer, conductor, pianist, organist, and academic teacher. Born in Brand, Bavaria, Reger studied music in Munich and Wiesbaden with Hugo Riemann. From September 1901 he settled in Munich, where he obtained concert offers and where his rapid rise to fame began. During his first Munich season, Reger appeared in ten concerts as an organist, chamber pianist and accompanist. He continued to compose without interruption. From 1907 he worked in Leipzig, where he was music director of the universityuntil 1908 and professor of composition at the conservatory until his death. In 1911 he moved to Meiningen where he got the position of Hofkapellmeister at the court of Georg II, Duke of Saxe-Meiningen. In 1915 he moved to Jena, commuting once a week to teach in Leipzig. He died in May 1916 on one of these trips of a heart attack at age 43.
He had also been active internationally as a conductor and pianist. Among his students were Joseph Haas, Sándor Jemnitz, Jaroslav Kvapil, Ruben Liljefors, George Szell and Cristòfor Taltabull.
Reger was the cousin of Hans von Koessler.