Christian August Sinding (11 January 1856 – 3 December 1941) was a Norwegian composer. He is known for his lyrical works for piano, such as Frühlingsrauschen (Rustle of Spring, 1896). He was often compared to Edvard Grieg and regarded as his successor.
He was born in Kongsberg to mine superintendent Matthias Wilhelm Sinding (1811–1860) and Cecilie Marie Mejdell (1817–86). He was a brother of the painter Otto Sinding and the sculptor Stephan Sinding. He was a nephew of Nicolai Mejdell (1822–1899) and Thorvald Mejdell (1824–1908), and through the former a first cousin of Glør Thorvald Mejdell, who married Christian's sister Thora Cathrine Sinding. Christian Sinding was also a first cousin of Alfred Sinding-Larsen and the three siblings Ernst Anton Henrik Sinding, Elisabeth Sinding and Gustav Adolf Sinding. Through his brother Otto he was the uncle of painter Sigmund Sinding.
In November 1898 he married actress Augusta Gade, née Smith-Petersen (1858–1936). She had been married to Fredrik Georg Gade for seventeen years, and was a daughter of Morten Smith-Petersen and maternal granddaughter of Jacob von der Lippe.
He studied music first in Christiania before going to Germany, where he studied at the conservatory in Leipzig under Salomon Jadassohn and fell under the musical influences of Wagner and Liszt. He lived in Germany for much of his life, but received regular grants from the Norwegian government. In 1920–21 he went to the United States of America to teach composition for a season at the Eastman School of Music in Rochester, New York. In 1924 he was given Henrik Wergeland's former home, "Grotten" ("The Grotto"), as an honorary residence. He died in Oslo.