The 28-year-old had a year remaining on his £100,000-a-week contract, but was deemed surplus to requirements with the Hammers board looking to cut the midfielder from their wage bill.
West Ham said in a statement: "West Ham United can confirm that the Club has agreed with Jack Wilshere to a mutual termination of the midfielder's contract.
"The 28-year-old departs having played 19 times and scored once since joining the Hammers in the summer of 2018. Everyone at West Ham United would like to wish Jack all the best for his future career."
Wilshere also confirmed the news on Twitter.
Wilshere's time at London Stadium was ravaged by injury, restricting him to just 19 appearances totalling 599 minutes, but he worked his way back to full fitness this season and played the entirety of last month's Carabao Cup win over Hull.
However, manager David Moyes did not view Wilshere has part of his plans -- having not selected him in any Premier League matchday squad -- and the England international will now look to begin a new chapter elsewhere.
Wilshere joined Arsenal at the age of nine, but left two years ago to join West Ham on a free transfer. He has hinted at one day playing abroad with sources telling ESPN Wilshere would consider playing in the United States.
Wilshere has earned 34 caps for England, but his last appearance came in the Euro 2016 last 16 defeat to Iceland.