Sam Allardyce will leave relegated West Bromwich Albion when their ill-fated Premier League campaign ends on Sunday.
Albion boss Allardyce confirmed his departure immediately after Wednesday's 3-1 home defeat against West Ham.
The 66-year-old held talks over his future with Albion hierarchy following their relegation earlier in May.
Allardyce said an offer was made for him to stay in charge in the Championship next season, but he will leave after Sunday's final match at Leeds.
The former England coach replaced the sacked Slaven Bilic in December but had a break clause in his contract which could be activated if Albion slipped into the second tier.
It was the first time Allardyce had been relegated from the top-flight in his managerial career.
"West Bromwich Albion made me a generous offer to stay at The Hawthorns that shows the commitment of an ambitious club. After serious consideration I have decided not to accept that offer," Allardyce said.
"If I were to stay and achieve promotion next season the expectation would be for me to continue for at least another season and, sadly, that is not a commitment I feel able to make at this stage of my career.
"I believe the club now needs stability and continuity and this would, in my opinion, best be provided by a young and ambitious manager who can get us back to where we should be as an established Premier League football club."
Albion are second bottom of the Premier League and have won five games all season.
West Brom sporting and technical director Luke Dowling said: "Sam came in at a really difficult time for the football club and worked tirelessly to keep the club in the Premier League.
"Ultimately, we were unable to accumulate the points total required to keep us here, but Sam certainly restored pride with a number of resilient displays.
"Sam, Ken (Chief Executive, Xu Ke) and I have discussed at length our plans for the future and we very much hoped to have Sam in charge for next season and beyond.
"Sam has given his reasons for leaving and we respect his decision."