Riley D. Herbst is an American professional stock car racing driver. He competes full-time in the NASCAR Xfinity Series, driving the No. 98 Ford Mustang for Stewart–Haas Racing and part-time in the NASCAR Cup Series, driving the No. 15 Ford Mustang Dark Horse for Rick Ware Racing.

Stewart–Haas Racing is an American professional stock car racing team that currently competes in the NASCAR Cup Series and the NASCAR Xfinity Series. The team is co-owned by three-time NASCAR Cup Series champion Tony Stewart and Haas Automation founder Gene Haas. It was founded in 2002 as Haas CNC Racing after Haas, whose company was a sponsor of Hendrick Motorsports, elected to form his own team. In 2009, Stewart, who had been driving for Joe Gibbs Racing, made a deal with Haas to drive for the team and in return receive a 50% stake in it.