卡尔·奥古斯特·尼尔森（丹麦语：Carl August Nielsen，1865年6月9日－1931年10月3日），丹麦作曲家和指挥家。

卡尔·尼尔森出生于欧登塞南部小村庄Sortelung的一个贫穷画家和油漆匠之家，他的父亲会演奏小提琴。他在十二个孩子中排第七。8岁的时候他就在他父亲和当地的一位教师那里学习小提琴。但很快他就转到吹奏乐器上面，而且在一个军乐队里供职14年。这段日子在他的自传《菲英岛上的童年》(1927年)里面有所描述。

1883年他到哥本哈根皇家音乐学院学习。他的专业是小提琴，并曾得到过作曲家如尼尔斯·加德的鼓励。1888年他的初次创作弦乐小组曲 op.1获得成功。1889年他成为哥本哈根皇家剧院小提琴手。而他获得了一份奖学金，使得在1890年他可以去到德国深造。

Carl August Nielsen (Danish: [kʰɑːl ˈnelsn̩]; 9 June 1865 –3 October 1931) was a Danish musician, conductor and violinist, widely recognized as his country's greatest composer. Brought up by poor but musically talented parents on the island of Funen, he demonstrated his musical abilities at an early age. He initially played in a military band before attending the Royal Danish Academy of Music in Copenhagen from 1884 until December 1886. He premiered his Op. 1, Suite for Strings, in 1888, at the age of 23. The following year, Nielsen began a 16-year stint as a second violinist in the prestigious Royal Danish Orchestra under the conductor Johan Svendsen, during which he played in Giuseppe Verdi's Falstaff and Otello at their Danish premieres. In 1916, he took a post teaching at the Royal Academy and continued to work there until his death.