Former NBA Most Valuable Player Kevin Durant, the biggest prize on the free agent market, announced on Monday that he will join the Golden State Warriors.

A four-times league scoring champion and seven-times All-Star who spent the first nine years of his career with the Oklahoma City Thunder franchise, the 27-year-old forward said in a piece posted on the Players' Tribune website that it has been the most challenging time of his professional life.

"The primary mandate I had for myself in making this decision was to have it based on the potential for my growth as a player -- as that has always steered me in the right direction," Durant wrote.

"But I am also at a point in my life where it is of equal importance to find an opportunity that encourages my evolution as a man: moving out of my comfort zone to a new city and community which offers the greatest potential for my contribution and personal growth."

"With this in mind, I have decided that I am going to join the Golden State Warriors."

Durant, whose former Thunder team came one win short of reaching the 2016 NBA Finals, met with Oklahoma City, Golden State, Los Angeles Clippers, Boston Celtics, San Antonio Spurs and Miami Heat before making his decision.

He joins a Warriors team that includes reigning league MVP Stephen Curry, won the NBA title in 2015 and finished runner-up in 2016 after a remarkable campaign in which they had a record 73 wins during the 82-game regular season.

Terms of the deal were not disclosed but Durant is reportedly expected to sign a two-year, $54.3 million contract with the Warriors.

The Warriors are still licking their wounds after slumping to a 4-3 NBA finals defeat to LeBron James and the Cleveland Cavaliers last month.

The 6ft 9in (2.06-meter) Durant took the Thunder to the brink of victory against Golden State in the Western Conference finals earlier last season, inspiring his team to a 3-1 series lead before the Warriors fought back to win 4-3.