Bay Port's winning streak has ended at 27 games.
Notre Dame topped the Pirates, 43-36, in a FRCC match-up on Tuesday.
The Tritons led 30-24 at the half and held on for the seven-point victory.
Notre Dame was led by 6-foot junior Maggie Gallagher, who scored a career-best 14 points, all coming in the first half.
Gallagher entered the game averaging under four points per game, but picked a great time for breakout.
Fellow junior Sammy Opichka, a 5-foot-11 point guard, added 10 points for coach Sara Rohde and the Tritons.
Bay Port was led by 6-foot-1 senior forward Mady Draak, a Michigan Tech signee, who scored 12 points.
Sophomore Emma Krueger, a 5-foot-7 guard, added 8 points for coach Kati Coleman and the Pirates.
Senior Mackenzie Johnson, a 5-foot-5 guard, was held to six points. Johnson netted 22 points in a 63-48 win in the teams' first meeting.
Bay Port, the top-ranked team in the Division 1 WSN Coaches Poll, entered the game at 19-0 before falling for the first time since February 8, 2019 when the Pirates dropped a 61-53 contest against Green Bay Preble.
Notre Dame, tied for No. 10 in the WSN Coaches Poll, improves to 14-6 overall and 12-4 in the FRCC. The Tritons' next game is at home against De Pere on Friday.
Bay Port drops to 19-1 overall and 15-1 in the FRCC. The Pirates can clinch the outright league title with a win over Green Bay Southwest on Friday.
Both teams have their sights set on a deep tournament run this season.
Bay Port is the reigning Division 1 state champions and the favorite in its sectional. The Pirates' top contender in their sectional is Kimberly. Last season, they defeated the Papermakers in a state semifinal.
Notre Dame, despite dropping two of its three games prior to Tuesday's win, is a team that is capable of a return trip to the Resch Center. The Tritons sectional does, however, feature three-time defending Division 2 state champion Beaver Dam, amongst others. Notre Dame fell to Beaver Dam in a sectional final last season.
Fall River extended its winning streak to 19 games on Tuesday.
The Pirates led 25-19 at the break against Rio before using a 16-1 run in the second half and cruised the rest of the way for the 52-38 win.
Senior Alexis Rozinski, a 5-foot-8 wing, scored a team-high 15 points for the Pirates.
Fellow senior Sam Leisemann, a 6-foot forward, added 14 points for coach Jim Doolittle and the Pirates.
Rio was led by junior Adeline Hutzler, a 5-foot-9 wing, who scored a game-high 16 points for coach and mother Deb Hutzler.
Fall River held freshman Emily Loging, a 6-foot-1 wing/forward, to five points. She entered the game scoring better than 10 points per contest.
Fall River moved to 19-1 overall and 13-0 in the Trailways West. The Pirates are the outright champions of the league. Their next game is at Princeton/Green Lake on Friday.
The Pirates, a Division 5 state qualifier last season, will have to deal with defending D5 state champion Black Hawk in sectional play this season after the Warriors were moved into their sectional for this season.
Rio drops to 8-12 overall and 6-7 in the Trailways West. The Vikings travel to Markesan on Friday.