Frank Anthony Castillo (April 1, 1969 – July 28, 2013) was an American Major League Baseball starting pitcher.

Castillo played for the Chicago Cubs (1991–1997), Colorado Rockies (1997), Detroit Tigers (1998), Toronto Blue Jays (2000), Boston Red Sox (2001–2002, 2004), and Florida Marlins (2005).

On September 25, 1995, in a 7–0 shutout victory over the St. Louis Cardinals at Wrigley Field, Castillo had a no-hitter broken up with two out in the ninth inning by inches.

[3] His most productive season came in 1995, when he posted career numbers in wins (11), earned run average (ERA) (3.21) and shutouts (2), while matching a career-high 135 strikeouts in 188 innings pitched.

Castillo briefly retired from Major League Baseball after receiving a World Series ring as a member of the 2004 Boston Red Sox.