West Ham had hoped that Moyes would stay on as manager for next season with David Gold stating on Monday that he “enjoyed working with him”.
But they are now on the lookout for a new boss with the club confirming they have come to a mutual decision for Moyes to leave.
West Ham held talks with Shakhtar Donetsk boss Paulo Fonseca earlier this week while former Manchester City manager Manuel Pellegrini is among the favourites to take over.
Hammers joint-chairman David Sulivan revealed in a statement on the club website that a new manager will be appointed within 10 days.
The statement read: “I would like to place on record my sincere thanks to David Moyes and his staff for achieving the target of keeping West Ham United in the Premier League.
“Throughout his time here, David has carried himself with dignity and honesty and we have all found him to be a pleasure to work with. He, Alan, Stuart and Billy accepted the challenge and attacked it head on, turning around a difficult situation. They deserve great respect for the job they have done and they leave the Club with our best wishes.
“When David and his team arrived, it was the wish of both parties that the focus be only on the six months until the end of the season, at which point a decision would be made with regards to the future. Having taken stock of the situation and reflected now the campaign is complete, we feel that it is right to move in a different direction.
“We are already taking steps to identify and recruit the manager we believe can take West Ham United forward in line with our ambitions. We aim to appoint a high-calibre figure who we feel will lead the Club into an exciting future for our loyal supporters within the next ten days.”
Moyes took over at West Ham in November after Slaven Bilic was sacked following a worrying start to the season.
The 55-year-old was able to steer the Hammers to safety with two games remaining but was not popular among most fans.