The Hawkeyes fell to no. 23. Iowa was previously ranked no. 18 is last week's poll.
Iowa mounted a fourth-quarter rally against Wisconsin, scoring 16 points in the quarter. They scored a touchdown late to bring it within two, but Nate Stanley's run on the two-point conversion attempt fell a yard short. Wisconsin held on to win 24-22.
Iowa is 6-3 overall and 3-3 in the Big Ten. The loss eliminated them from the Big Ten West title race.
The Hawkeyes are back home next Saturday against an undefeated Minnesota team. That game kicks off at 3 p.m. on FOX.
The second week of the College Football Playoff Rankings will come out on Tuesday.
AP Top 25 Rankings:
2 Ohio State
9 Penn State
16 Notre Dame
19 Boise State
25 Oklahoma State