She led the nation in scoring for the second consecutive year and is the first player from the school and the Big Ten to win the award.
The 6-foot-3 star received 15 votes Thursday from the 28-member national media panel that selects the weekly AP rankings. Balloting was done before the NCAA Tournament.
Sabrina Ionescu of Oregon received seven votes while Napheesa Collier of UConn three. Asia Durr of Louisville had two votes and Teaira McCowan of Mississippi State one.
Gustafson averaged 27.9 points and helped the Hawkeyes reach the Elite Eight for the first time since 1993. She became only the fourth Division I player to score more than 1,000 points in a season. She tied the NCAA record for double-doubles in a season with 33.