Fernando Tatís, Jr. (born January 1, 1975) is a Major League Baseball utility player for the New York Mets. He previously played for the Texas Rangers (1997–1998), St. Louis Cardinals (1998–2000), Montreal Expos (2001–2003), and Baltimore Orioles (2006). He bats and throws right-handed. Tatís is the only player in Major League Baseball history to hit two grand slam home runs in one inning.

At 17 years old, Tatís was signed as an amateur free agent by the Texas Rangers on August 25, 1992. He made his Major League Baseball debut with the Rangers at third base almost five years later on July 26, 1997 and would go on to play 60 games with the Rangers in his rookie season. At the trade deadline on July 31, 1998, the Rangers traded Tatís along with Darren Oliver and Mark Little to the St. Louis Cardinals for Royce Clayton and Todd Stottlemyre.

Tatís enjoyed a career year in 1999 with the St. Louis Cardinals, when he hit 34 home runs with 107 RBI and 21 stolen bases while posting a .298 batting average. On April 23, 1999, Tatís made history by hitting two grand slams in a single inning. He hit both against Chan Ho Park of the Los Angeles Dodgers. With this feat, Tatís also set a Major-League record with eight RBI in a single inning. After only playing in 96 games in 2000 due to injury, Tatís was traded to the Montreal Expos with Britt Reames for Dustin Hermanson and Steve Kline. Unfortunately for the Expos, Tatís would only play in 208 games over the span of three seasons for them due to various injuries and time on the disabled list.