Former Sunderland boss David Moyes admits he has a point to prove and faces a big job to win over West Ham's supporters.
The 54-year-old Scot, who resigned as Sunderland manager following relegation from the Premier League, has been confirmed as new Hammers manager less than 24 hours after Slaven Bilic was sacked with the club in the relegation zone.
Many fans are underwhelmed by the appointment, with Moyes having failed to save Sunderland from relegation last season as well as enduring disappointing spells with Manchester United and Real Sociedad.
Yet his successful 11-year stint as Everton boss has persuaded Hammers joint-chairmen David Sullivan and David Gold that Moyes is the man to turn their season around.
Moyes told the West Ham website: "Do I have a point to prove? Yes, I think I do.
"I've managed five clubs since starting out nearly 20 years ago, starting at Preston and then going to Everton.
"My period at Manchester United is well documented and I then did something I have always wanted to do by experiencing management abroad, with Real Sociedad.
"It's only been the last job where I feel it wasn't a good move and I didn't enjoy the experience. So I'm hungry to make sure I get things right now.
"The focus here is purely between now and the end of the season. The first thing is to win the next game and build from there, and I'm sure we will be in a much stronger position before long."
Moyes has taken training on Tuesday and has almost a fortnight to get to know his new players, with his first match in charge at Watford on November 19.
Sullivan told the club website: "This is a unique position for David Gold and myself - it is the first time in almost eight years at West Ham United that we have appointed a new manager during the season.
"We need somebody with experience, knowledge of the Premier League and the players in it, and we believe David is the right man to turn things around and get the best out of the players at the club.
"He is highly regarded and respected within the game, and will bring fresh ideas, organisation and enthusiasm.
"He proved with Everton that he has great qualities and we feel that West Ham United is a club that will give David the platform to display those qualities again."