Karel Weis was a Czech composer and folksong collector. He was born in Prague. Weis studied at the Prague Conservatory from 1873–1878, the Prague Organ School from 1878–1881, and privately with Zdeněk Fibich. He was organist of St Štěpán and choirmaster at the main synagogue of Prague (1881–1882), a teacher at the music school of the Moravan choral society in Kroměříž (1882–1883), a violinist in the National Theatre orchestra, Prague (1883–1886) and conductor of the Švanda Theatre Company in Prague and Brno (1886–1887). Subsequently he edited the monthly Hudební květy (1895–1899), conducted the Academic Orchestra (1898) and worked as an accompanist (1896–1904), mainly for the violinist František Ondříček.