He replaces Wyking Jones, who was fired last week after just two seasons in Berkeley.
"Mark Fox is a man of unparalleled integrity with a proven record of success as a head basketball coach," Cal athletic director Jim Knowlton said in a statement. "He is an inspiring leader, a teacher and an exceptional communicator who has displayed a strong commitment to developing the entire student-athlete on the court and off the court.
"We had an exceptional pool of candidates, and through the entire process, one person clearly rose to the top. I am excited to welcome Mark to the Cal family and look forward to him leading Cal men's basketball program to new heights. We want our teams to be exceptional, and I firmly believe that Mark is the person to lead us there."
Fox was fired by Georgia after last season after nine seasons with the Bulldogs in which he made two NCAA tournaments. He had more success during his five seasons at Nevada, leading the Wolf Pack to four regular-season WAC titles and three NCAA tournament appearances, advancing past the first round on two occasions.
"Early in my coaching career, I had the privilege to spend time with coach Pete Newell. It will be my honor to lead the Bears on the court gracing his name," Fox said in a statement. "The lineage of greatness of the Pac-12 offers a tremendous platform for Cal basketball."