Samuel "Sam" Mayer (born June 26, 2003) is an American professional stock car racing driver, currently competing full-time in the NASCAR Xfinity Series for Haas Factory Team. The son of former IndyCar driver Scott Mayer, Sam began his racing career at age four in go-karts before shifting his focus to stock cars. He achieved remarkable early success, winning the Young Lions division of the Charlotte Motor Speedway Summer Shootout at 14 and becoming the youngest NASCAR champion in 2019 by securing the K&N Pro Series East title at 16 years old.

Mayer continued his dominance in 2020, claiming both the East Series championship again and the inaugural ARCA Menards Series Sioux Chief Showdown title. A significant highlight of his ascent was his "sweep" at Bristol in 2020, where he famously won both the Truck Series and ARCA races on the same night, solidifying his reputation as a formidable young talent in NASCAR.