Paul August von Klenau (11 February 1883 in Copenhagen – 31 August 1946 in Copenhagen) was a Danish-born composer who worked primarily in Germany and Austria.
Klenau was born in Copenhagen, where he studied under Otto Malling. Already as a young man he left his native country to study and work in Germany and Austria, among others with Max Bruch, Ludwig Thuille and Max von Schillings. His first, Bruckner-influenced symphony was premiered successfully in 1908 at a Tonkünstlerfest in Munich. Within just five years the three additional large-scale symphonies followed. Later influences include French music, Richard Strauss, and Arnold Schoenberg's twelve-tone technique. Klenau was among Arnold Schoenberg's advocates during the 1920s, and Schoenberg attended a concert of his music conducted by Klenau in 1923 in Freiburg. He also belonged to Alban Berg's circle of friends.
Klenau never achieved full recognition as a composer in Denmark, but he sat in a number of important conductor positions. In 1912, he led the concerts of the Bach Society Frankfurt, but already the following year he returned to the conductor position at the Freiburg opera. He took up permanent residence in Bavaria, where he owned a country house, but as a conductor he traveled extensively, both in Germany and the United Kingdom. His summers were spent in Denmark. In 1922, he became a choral conductor at the Vienna Konzerthausgesellschaft, where he served until 1930, the last six years as Konzertdirektor.