Halfdan Magnus Mustad (9 June 1874 – 21 January 1967) was a Norwegian businessman. He was born in Vardal as the son of Hans Mustad and Marie Heyerdahl. On the maternal side he was a great-grandson of Hieronymus Heyerdahl, and on the paternal side he was a grandson of Ole Hovelsen Mustad, great-grandson of Hans Schikkelstad, nephew of Kristian Mauritz Mustad and cousin of Sigbjørn Mustad. Halfdan Magnus Mustad married Edle Smith in 1899, and the couple had several children. They settled at Lysaker in Bærum.