Grant has signed a four-year contract with the Premier League side, subject to a work permit.
Grant told the club’s official website: “I am proud and honoured to be the manager of West Ham. It will be an exciting challenge and I am ready to do my best.
“This is a fantastic club with great fans and a history that is respected around the world. I am already looking forward to getting to work with my players in July and preparing for the new season.”
West Ham co-owners David Gold and David Sullivan is delighted with the new manager.
Gold said: “I have to say that having met Avram and spent some time with him that we have got our man. He is a perfect fit.
“We needed experience and stability. He is a footballing man and quite frankly his reputation speaks for itself. He has a great sense of humour and I am sure the players will relate to him and the fans will warm to him.”
And Sullivan added: “I am delighted to welcome Avram to West Ham and am confident he will prove a success. We have taken our time over this appointment and are certain we have got the right man.
“We are all looking forward to next season with new players coming in and Avram’s arrival is just the latest reason for real optimism.”