Jacob Adolf Hägg (29 June 1850, Östergarn – 1 March 1928, Bjuråker) was a Swedish composer. Hägg studied piano at the Stockholm Conservatory from 1865 to 1870, as well as composition in Copenhagen with Niels Wilhelm Gade and in Berlin with Friedrich Kiel. Due to mental illness, he spent the years 1880 to 1895 in a hospital. He then worked as a pianist and composer in Hedvigsfors, Sweden, and continued to do so after moving to Norway between 1900 and 1909 and resettling in Sweden at Hudiksvall. His cousin Gustaf Hägg (1867–1925) was also a composer.