“The club would like to place on record its thanks to Tony and Mark for their efforts – but has made the decision to part company following a series of poor results,” a short Albion statement said.
“Tony and Mark will forever be welcome at The Hawthorns and their contributions to the club winning the 2007-08 Championship title will never be forgotten.”
Mowbray, who led the Baggies to the Premier League 17 years ago, had returned to management for the first time since a health scare in February 2024.
That led to him stepping away from his role in charge of Birmingham City to undergo treatment for what was later revealed to be bowel cancer.
He was unable to recreate the success he had in his first spell as Albion boss, when he steered West Brom to the Championship play-off final in his first season in charge although they were beaten by Derby County at Wembley.
But a year later they won the title, having also reached the FA Cup semi-final where they lost to eventual winners Portsmouth.
Relegation followed after one season in the top flight, after which Mowbray left in 2009 for Celtic Park.
He had five more managerial stints, with his hometown club Middlesbrough, Coventry City, Blackburn, Sunderland and Birmingham before returning to The Hawthorns.
