Moyes stepped into the helm following the sacking of Slaven Bilic in November with the sole objective of keeping the 'Hammers' in the Premier League.
The former Manchester United manager managed it, securing a 13th-placed finish, but it wasn't enough for the board to extend his contract.
In a club statement, joint-chairman David Sullivan said: "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.
"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."
Speculation has indicated that Shakhtar Donetsk manager Paulo Fonseca is the frontrunner to be Moyes' replacement.
16 May 2018