Sunderland have appointed Sam Allardyce as manager on a two-year contract.
Dick Advocaat quit Sunderland on Sunday with the Black Cats second-bottom of the Premier League and winless in their opening eight games.
Allardyce, 60, has been out of management since he left West Ham at the end of last season.
"Of course it's a challenging job. But I hope to be able to help to bring the stability and success that everyone wants," Allardyce said.
"I'm looking forward to working with the players and of course I will be relying on the help of the Sunderland supporters."
Allardyce had a spell at Sunderland as a player between 1980 and 1981 and becomes the first person to manage both the Black Cats and rivals Newcastle.
His first home game at the Stadium of Light will be against Newcastle on 25 October, with an away trip to West Brom before that on 17 October.
Sunderland owner Ellis Short believes Allardyce, who managed Newcastle from May 2007 until January 2008, was the standout candidate for the job.
"Sunderland is a club he knows well and he was the obvious best choice for the job," Short said.
"He has vast experience of managing in the Premier League and an understanding first-hand of the north-east and the passion of our fans, which will stand him in great stead."
|Sam Allardyce's Premier League record|
'Sam understood the importance of this job'
Short also claimed it was a "misconception" that the former Blackburn and Bolton boss "had to be persuaded to join us".
"This was a very popular job, proactively sought after by a large number of managers - contrary to much of what has been portrayed," Short said.
"The process was made easier by the fact that Sam was such an obvious choice.
"From the very beginning, Sam understood the importance of this job and showed great enthusiasm for the role and a desire to be part of moving this club forward."