Mayfield, a senior, will also not serve as a captain on Oklahoma's senior day.
"This decision was difficult," said Riley, who became emotional during his weekly press conference, unable to speak for several seconds.
During the third quarter in Lawrence, Mayfield grabbed his crotch and appeared to yell "F--- you!" at the Jayhawks' sideline.
Mayfield, the frontrunner to win the Heisman Trophy, apologized to reporters and over social media after the game Saturday night.
"I got caught up in a competitive game, a chippy game, but what I did was unacceptable," Mayfield said. "I apologize. It's disrespectful. It's not the example I want to set. It's not the legacy I want to leave at OU. I truly do apologize. Thinking about the kids that are watching this now, it's not something I want to do to the parents out there. I'm sorry."
Riley declined to disclose when Mayfield might enter the game against the Mountaineers.
"I'm proud as hell to be his coach," Riley said. "This darn sure shouldn't taint all the great things he's accomplished here on and off the field."