Baltazar Mathias Keilhau (2 November 1797 – 1 January 1858) was a Norwegian geologist and mountain pioneer. He was born in Gjøvik. In 1830 he married Christine Kemp. Keilhau is regarded as the founder of geology in Norway. He lectured at the Royal Frederick University in Christiania from 1826, and was appointed professor from 1834.