The former Juventus man has become disillusioned with life at Stade Velodrome, and is unhappy about the lack of funds available to strengthen the squad
The former France international has been in charge at Stade Velodrome since 2009, and led the club to Ligue 1 glory in his first season in the job.
However, OM endured a torrid league campaign last season, managing a 10th place finish, with financial troubles dogging the club.
And Deschamps has admitted that he has been looking for a way out for more than a month, and feels that his exit would work best for both parties.
"You should know that the directors of Marseille have known my position since May 25 after a meeting in Paris," he told Le Phoceen.
"I am someone [who] always behaves well and will always be respectful to the club. I know what it means to me.
"I've taken this decision because it's impossible to work under these conditions. It would have been detrimental for both the clubs and players."