The resignation was reported first by WWL-TV in New Orleans Friday night. The station said Williams resigned to pursue other career interests.
The New Orleans Times-Picayune reported Saturday that Williams will become an assistant at Marquette under Coach Tom Crean.
His decision was confirmed by UNO Director of Athletics Jim Miller.
Williams guided the Privateers to a 14-17 overall record last season. They were 9-9 in the Sun Belt Conference.
"I am extremely disappointed that Buzz Williams has decided to resign," Miller said. "But it's his decision on what to do with his career, whatever the reasons. He has made giant strides at improving our program, for which we are grateful."
Williams succeeded Monte Towe, who also stayed one season, and then became an assistant at North Carolina State under former college teammate Sidney Lowe.