Jonathan Henry Jay (born March 15, 1985) is an American professional baseball coach and former outfielder who is an assistant coach for the St. Louis Cardinals of Major League Baseball (MLB). He played in MLB for the St. Louis Cardinals, San Diego Padres, Chicago Cubs, Kansas City Royals, Arizona Diamondbacks, Chicago White Sox, and Los Angeles Angels.

A product of the University of Miami, Jay played college baseball for the Miami Hurricanes. He was the Cardinals’ second (of three) second-round selection(s) (74th overall), in the 2006 MLB draft. Through the end of the 2020 season, Jon Jay has the third highest modern-day career fielding percentage for a center fielder at .996, behind only Darin Erstad and Shane Victorino.

Jay made his big league debut for the Cardinals in 2010, after batting .301, with 4 home runs (HR), a .780 on-base plus slugging percentage (OPS), and 2 stolen bases (SB), in 105 major league games. The starting center fielder for four consecutive National League Championship Series (NLCS)-qualifying clubs as a Cardinal (2011−14), he was a World Series champion in 2011, as the Cardinals defeated the Texas Rangers. Between 2011 and 2013, Jay established an errorless record streak for National League (NL) center fielders at 245 games. In 2012, he finished tenth in the NL in both batting average and on-base percentage (OBP).

After wrist injuries limited Jay's effectiveness in 2015, he was traded to the Padres. Always active in the community, Jay has hosted celebrity bowling tournaments for charity. He signed a one-year US$4M contract to play the 2019 season with the Chicago White Sox.

Jay was born in Miami, Florida, and spent his youth there. His parents immigrated to the United States from Cuba—his mother from Matanzas and his father from Santiago in the 1960s. He is of distant Spanish descent. His father, Justo Jay, spent 19 years in prison for his role in the cocaine trafficking organization of Sal Magluta and Willy Falcon. Jay attended George Washington Carver Middle School and Christopher Columbus High School.

Showing exceptional baseball skill in high school, Jay played on the state championship-winning team during his senior year in 2003. He received a scholarship at the University of Miami and played for the Miami Hurricanes baseball team. During his three years at UM, Jay had a combined .387 batting average (BA), with 31 doubles (2B), four triples (3B), seven home runs (HR), and 108 runs batted in (RBI), in 120 games played (G). In 2005, he played collegiate summer baseball with the Brewster Whitecaps of the Cape Cod Baseball League. The Cardinals selected him in the second round (74th overall) of the 2006 MLB draft.

After signing with St. Louis, Jay made his professional debut that year with the Swing of the Quad Cities and spent the whole season there, slashing .342/.416/.462, with three HR and 45 RBI in 60 games. In 2007, he played with the Palm Beach Cardinals, where he batted .286, with two homers and ten RBI in 32 games, and the Springfield Cardinals, where he posted a .235 average, two HR, and 11 RBI in 26 games. Jay began 2008 with Springfield, and after batting .306/.379/.457, with 11 HR, and 47 RBI, in 96 games, he was promoted to Memphis where he ended the season with a .345 batting average, one HR, and ten RBI, in 16 games. Jay spent 2009 with Memphis, where he compiled a .281 batting average, with ten HR, 54 RBI, and 20 stolen bases in 136 games. He began 2010 with Memphis.

Jay made his Major League debut on April 26, 2010 with the St. Louis Cardinals, after having begun his second consecutive season with the Memphis Redbirds. During his rookie season, he played in 105 games and made 323 plate appearances (PA), batting .300, with 19 doubles, and a .359 on-base percentage (OBP). In the outfield, Jay played all three positions. Stationed mainly in right field, he collected five assists.