Roscoe Tanner (born October 15, 1951) is a retired American professional tennis player, who turned pro in 1972 and reached a career-high world singles ranking of World No. 4 on July 30, 1979.
Tanner was famous for his big left-handed serve, which was clocked at 153 mph at Palm Springs in 1978 during the final against Raúl Ramírez.He is also known for winning the men's singles title at the first of two Australian Open tournaments held in 1977. Tanner won the tournament held in January, Vitas Gerulaitis won the December tournament. Tanner reached the Wimbledon final in 1979, losing to Björn Borg in five sets.
Tanner was in the news in the 2000s for legal problems that included stretches of imprisonment, arrests for missing child support payments, allegations of financial misdeeds, and bankruptcy.
Leonard Roscoe Tanner III hailed from Lookout Mountain, Tennessee, graduated from Baylor School in Chattanooga, and with teammate Sandy Mayer helped to lead Stanford University's rise to national prominence in collegiate tennis. Tanner played number one singles, with Mayer playing number two. In 1972, Tanner and Mayer won the NCAA doubles championship, and the Stanford team finished second in the NCAA tournament, behind Trinity (TX). The team also featured Chico Hagey, Rick Fisher, Jim Delaney, Gery Groslimond, Chip Fisher, Paul Sidone, and Tim Noonan.