West Ham hired Nuno Espirito Santo as their new manager just hours after sacking Graham Potter on Saturday.
Nuno, axed by Nottingham Forest earlier this season, agreed a three-year contract with the Premier League strugglers and will take charge of his first game at Everton on Monday.
Potter's exit, which came only nine months after his appointment, was widely expected after the Hammers slumped to second bottom of the table, AFP reported.
"I am very pleased to be here and very proud to be representing West Ham United," Nuno, 51, said.
"My objective is to work hard to get the very best from the team and ensure that we are as competitive as we possibly can be.
"The work has already started and I am looking forward to the challenge that is ahead."
Former Tottenham and Wolves boss Nuno was dismissed by Forest owner Evangelos Marinakis three weeks ago after the pair fell out over the club's transfer policy.
Nuno had earned praise for lifting Forest into European competition for the first time in 30 years last season via a seventh-place finish in the Premier League.
The Portuguese coach also impressed at Wolves, helping establish them in the top-flight before leaving for a turbulent 17-match spell at Tottenham that ended in the sack.
Potter managed just three points from West Ham's five league matches this season, while they also crashed out of the League Cup against Wolves.
The former Chelsea and Brighton manager only took the reins at the London Stadium in January, with last season's disappointing 14th place finish putting pressure on him to hit the ground running this season.
Last weekend's home defeat against Crystal Palace proved the final straw.
Potter, who lost five of West Ham's six games this season, was relieved of his duties less than 24 hours after holding his usual pre-match press conference on Friday.
"Results and performances over the course of the second half of last season and the start of the 2025/26 season have not matched expectations," West Ham said in a statement.
"The board of directors believe that a change is necessary in order to help improve the team's position in the Premier League as soon as possible."
Potter won only six of his 25 West Ham matches after replacing Julen Lopetegui, who lasted just 22 matches after taking over from David Moyes, who is now in charge of Everton.
Despite Potter's substantial spending on eight new signings in the summer transfer window, West Ham made a woeful start to the season.
A 3-0 win at Nottingham Forest last month provided some respite, but West Ham went down by the same score to Tottenham after the international break before the Palace loss heralded the end of his dismal spell in charge.
In a statement released soon after his dismissal, Potter hinted he felt he deserved more time.
"I am incredibly disappointed to be leaving West Ham United Football Club, particularly without being able to achieve what we set out to achieve at the start of our journey in East London," said Potter, who lasted less than seven months before being axed as Chelsea boss in 2023.
"I do however fully acknowledge that the results have just not been good enough up to now."
