The resignation comes after Gallagher led her team to a 31-24 overall record this spring. The Badgers won 18 of 20 games late in the year to earn an invitation to the NCAA tournament, their third such trip during Gallagher's tenure. The Badgers hosted one of the NCAA Regionals and fell to No. 23 DePaul and No. 6 Oregon State to conclude the season.
"It is time for a new chapter in my life," Gallagher said in the release. "My time at the UW has been very rewarding and I'm proud of the things we've accomplished. But I'm ready to step aside from the Badger program to pursue some other opportunities."
Gallagher, a former assistant at California, was hired Aug. 29, 1994 and took the field for the first time in the spring of 1996, all with players and staff she recruited. Gallagher finished her UW career with a 271-268-2 record and an 85-121 mark in the Big Ten. Gallagher's players earned 15 All-Big Ten awards, including star pitcher Andrea Kirchberg, who is the program's only All-American.
After a 31-22 finish in 2002, the softball team stumbled the next few seasons, finishing 19-26 in 2003 and 29-28 in 2004 before its dramatic rally to finish 31-24 in 2005.
"Karen started the program from scratch and did a number of good things in establishing some traditions for Wisconsin softball," UW athletics director Barry Alvarez said. "Three of her teams made the NCAA Tournament and five won at least 30 games. I want to express my appreciation for her hard work and for taking the program to where it stands today as a tournament qualifier."