Onstad is a Norwegian surname. Notable people with the surname include:
Chris Onstad, American writer, cartoonist, and artistErik Gjems-Onstad, Norwegian resistance member, lawyer, and politicianKari Onstad, Norwegian singer and actressKatrina Onstad, Canadian critically acclaimed journalist and novelistKenton Onstad, American politician, member of the North Dakota House of RepresentativesKristian Flittie Onstad, Norwegian professional footballer defenderNiels Onstad (1909-1978), Norwegian shipping executiveOle Gjems-Onstad, Norwegian juristOtto Onstad (1874-1961), American politicianPat Onstad, Canadian professional soccer goalkeeper