The Dudley-born boss was announced as the Baggies new head coach this evening – on the same day the club confirmed the sacking of Slaven Bilic.
Allardyce, who will be in charge for Sunday’s derby with Villa, will meet Albion’s squad and take training for the first time on Thursday.
Bilic was relieved of his duties after a successful 18 months at the helm in which he masterminded the clubs’ return to the Premier League.
But the Baggies have struggled since returning to the top flight with just one win in 13 league games.
The team also ended last season poorly despite achieving promotion – with Albion having won just 10 league matches in 2020.
That run of results prompted the board to relieve Bilic of his duties and turn to Allardyce – a man who is widely regarded as an expert at keeping teams in the Premier League.
Sporting and technical director, Luke Dowling, said: “In Sam we have a man who has a proven Premier League pedigree with a track record of improving every club he has managed.
“We believe and, more importantly, Sam believes we have a group of players that have the quality needed to give the club its best chance of Premier League survival.”
Despite the arrival of Allardyce, many fans have been left angered by Bilic’s departure.
The 52-year-old enjoyed a fantastic rapport with supporters.
And many fans feel with an initial summer transfer budget of just £20million, the Croatian needed more funds to have a realistic chance of keeping the team in the Premier League.
But the Express & Star understands club chiefs feel the team has been too easy to play against this season.
They also feel without the outstanding performances of goalkeeper Sam Johnstone, they would have even fewer points than the seven they have amassed.
Allardyce’s appointment means the 62-year-old’s career has gone full circle.
The former Bolton boss began his coaching career with the Baggies after being appointed the player-manager of the club’s reserve side in 1988.
He was then promoted by manager Brian Talbot to become a first-team coach.
Since then he has gone to enjoy a hugely successful managerial career.
Allardyce had transformational spells in charge of Bolton, Blackburn and West Ham.
He also defied the odds to keep Crystal Palace and Sunderland in the Premier League.
His career, though, has also featured some high profile lows off the pitch.
In July 2016, Allardyce was appointed England manager. But he left after one game following a newspaper sting claiming he offered advice on how to “get around” rules on player transfers.
As well as Bilic, Albion confirmed they have also parted company with assistant coaches, Dean Racunica and Danilo Butorovic, and first team coach Julian Dicks.