The 2014 MVP award winner will now team up with Stephen Curry, the two-time reigning MVP who is widely regarded as one of the best shooters in the league's history.
Durant made the announcement on Twitter, posting the link to his June 4 Players' Tribune piece titled My Next Chapter.
"This has been by far the most challenging few weeks in my professional life," the 27-year-old wrote of his free agency after ending his season with the Oklahoma City Thunder in defeat during the Western Conference Finals at the hands of none other than the Warriors squad he is now joining.
The decision was "based on the potential for my growth as a player" Durant said.
After spending his entire career with the team, the biggest prize in free agency acknowledged in his post that his decision would dash the hopes of many in Oklahoma who saw the Thunder come within one game of reaching the Finals.
"It really pains me to know that I will disappoint so many people with this choice, but I believe I am doing what I feel is the right thing at this point in my life and my playing career," he added.
The Thunder issued a statement in which chairman Clayton Bennett thanked Durant for his leadership, and praised his "profound" contributions.
Thunder General Manager Sam Presti said Durant made an "indelible mark" on the team and described him as "a founding father of this franchise".
Durant's announcement created ripples on social media that resonated with fans and fellow players alike.
"If u can't beat um join um," Paul Pierce of the Los Angeles Clippers wrote in a Twitter post retweeted more than 25,000 times.
The Warriors' Draymond Green welcomed Durant to "the family", saying, "let's just do what we are setting out to do!!"
According to ESPN's Marc Stein, Durant will sign a two-year, $54.3 million deal with his new team; however, no official details have been announced.
The Warriors made history last season with a 73-9 tally in the regular season, breaking a 72-win record by the Michael Jordan-led Chicago Bulls that held for two decades.
Golden State lost in the NBA Finals to the Cleveland Cavaliers that, led by LeBron James, won its first title as a franchise.
With the addition of Durant to the roster, the Warriors become an instant favorite as the team to beat in the Western Conference.
