Samuel Jon Hornish Jr. (born July 2, 1979) is an American semi-retired professional auto racing driver. He last competed part-time in the NASCAR Xfinity Series, driving the No. 22 Ford Mustang for Team Penske in 2017.

Hornish began his top-tier racing career in the IndyCar Series, making his driving debut during the 2000 season for PDM Racing. Hornish began driving for Panther Racing the following season, winning eleven races and the 2001 and 2002 series championships over the next three seasons. During the 2004 season Hornish began driving for Team Penske, winning eight more races (including the 2006 Indianapolis 500) and the 2006 series championship during his time with the team. When he left the series after the 2007 season, he held the record for most career wins in the series (19, broken by Scott Dixon in 2009).

Hornish moved to Penske's NASCAR program part-time in the Xfinity Series (then known as the Busch Series) during the 2006 season, and began driving part-time in the Cup Series (then known as the Nextel Cup Series) in 2007. He raced full-time in the Cup Series the following year, struggling at first, with eight top-ten finishes over his first three seasons and a top points placing of 28th (in 2009). Hornish returned part-time to the Xfinity Series (then known as the Nationwide Series) in 2011, winning one race. He drove full-time in the series the following year, finishing fourth in points. In 2012 Hornish replaced A. J. Allmendinger (suspended by NASCAR for failing a drug test) in Penske's No. 22 car midway through the season, earning one top-five finish. The following year he returned to the Nationwide Series, winning one race and earning sixteen top-five and 24 top-ten finishes to place second in points (three behind series champion Austin Dillon). Hornish drove part-time for Joe Gibbs Racing in an eight-race 2014 season, with one win and four top-five finishes. He returned to the Cup Series in 2015 with Richard Petty Motorsports, scoring three top-tens and finishing 26th in points. He returned part-time to the Xfinity Series in 2016, winning a race for JGR and finishing sixth or better in all three races he entered for Richard Childress Racing. In 2017, he returned to Penske's Xfinity program for a three-race schedule in the No. 22.

Hornish began racing go-karts at the age of eleven, winning the World Karting Association U.S. Grand National championship in less than four years. From 1996 to 1998, he made 32 starts in the U.S. F2000 National Championship. In Hornish's final season in the series, he had a career-best, second-place finish at Pikes Peak International Raceway. He finished seventh in points in 1998, and was inducted into the series' Hall of Fame in 2012 as a 1998 graduate. During the 1999 Atlantic Championship season Hornish drove for Michael Shank Racing team owner Mike Shank, winning at Chicago Motor Speedway and finishing seventh in the championship standings with 67 points.

During the 1999 United States Road Racing Championship season, Hornish drove for Intersport Racing in the United States Road Racing Championship at the season-opening Rolex 24 at Daytona with Jon Field, Ryan Jones and Mike Shank in the Can-Am class. Their car, starting in eighth place, finished 42nd (14th in its class) after retiring on lap 400 with a gearbox failure.

In 2007, Hornish returned to compete in the season-opening Rolex 24 at Daytona for Michael Shank Racing with Mark Patterson, Oswaldo Negri Jr., and Hélio Castroneves in the Daytona Prototype class. Their car started 22nd, in its class and overall. It finished ninth in its class and overall, completing 628 laps.

Hornish began driving in the IndyCar Series in 2000 for PDM Racing in the No. 18 G-Force GF05-Oldsmobile Aurora L47 V8. He debuted at the season-opening race at Walt Disney World Speedway, starting in nineteenth place and finishing in twentieth (28 laps behind). In the season's third race, the Vegas Indy 300 at Las Vegas Motor Speedway, Hornish started eighteenth and had his first career podium finish (third place, one lap behind). He qualified for his first Indianapolis 500 in fourteenth place, after his team replaced the G-Force with a Dallara IR00. In mid-race, Hornish was involved in an accident which relegated him to 24th place. Starting twentieth at Kentucky Speedway, he led for a series career-high 38 laps and finished ninth. Hornish ended his season with a 27th- (and last-) place finish at Texas Motor Speedway, finishing his rookie season with 110 points (21st in the point standings).

Before the 2001 Indy Racing League season, Hornish moved to Panther Racing to drive the No. 4 Dallara IR01-Oldsmobile Aurora L47 V8. He began the season with consecutive victories at Phoenix and Homestead-Miami in his first two races with the team. At the Indianapolis 500, Hornish qualified in thirteenth place. He finished fourteenth, four laps behind after an early spin. He continued to drive well, clinching the championship before the final race of the season (a second-place finish at Chicagoland Speedway). Since the winner of each race received fifty points, Hornish's 66-point advantage clinched the championship with one race remaining. At the season-ending race at Texas he started in the pole position, leading for 115 laps in his third win of the season. Hornish won the championship with 503 points, 105 points ahead of second-place Buddy Lazier. At age 22, he was the youngest champion in series history.