Nolan captained the Hammers to their promotion from the Championship in 2012 and was then the club’s top scorer in their first two seasons back in the Premier League.
The Liverpool-born midfielder leaves the club by mutual consent after four years, 157 games and 31 goals for the Hammers.
He played his final game in Saturday’s 4-3 defeat to Bournemouth but was substituted at half-time.
“I¹ve thoroughly enjoyed my time at West Ham United and will take some great memories with me. I¹m now looking forward to the next challenge playing for a new club,” said Nolan.