Twice All-Star outfielder Giancarlo Stanton has agreed to an eye-popping contract extension worth $325 million over 13 years with Major League Baseball's Miami Marlins, the most lucrative deal in US professional sport.

The mind-boggling move more than triples the previously biggest contract reached by the Marlins - $106 million spread over six years for Jose Reyes in 2012.

The deal also exceeds the previous MLB record of $292 million over 10 years agreed by Miguel Cabrera with the Detroit Tigers in March.

"This is a landmark day," Marlins owner Jeffrey Loria told by phone on Monday.

"I'm happy for the city. I'm happy for him. And I'm thrilled for baseball. We have a player who is committed to us, and we've committed to him for the life of his career. The deal includes a no-trade clause and Stanton, who is aged 25 and led the National League (NL) with 37 home runs last season, can opt out after six years."

A second-round pick by the Marlins in the 2007 MLB Draft, Stanton is one of the most feared power hitters in baseball and, despite playing his home games in the spacious surrounds of Marlins Park, has blasted 154 career homers.

He led the NL in slugging percentage (.555) for the 2014 season, finishing with a .288 batting average when his season ended prematurely after he was hit by a pitch in the face by Milwaukee Brewers pitcher Mike Fiers.

Stanton earned his first NL Silver Slugger Award and became the first Marlins player to win the Hank Aaron Award, which recognises the top offensive performer in each league and is voted on by fans and a panel of Hall of Fame players.

Source: Reuters