Hampus Wilhelm Arnell (2 August 1848 in Härnösand – 1932 in Uppsala) was a Swedish bryologist. He was the father of hepaticologist Sigfrid Vilhelm Arnell (1895–1970). In 1875, he became a privat-docent of botany at the University of Uppsala, later working as a schoolteacher in Umeå and Harnosand. In 1880 he became an associate professor of natural history and chemistry in Jönköping. He later taught classes in Gävle (from 1894) and Uppsala (from 1901). The liverwort genera Arnellia Lindb. and Arnelliella C. Massal. commemorate his name.