Paolo Di Canio has been appointed head coach of Sunderland.
The 44-year-old Italian, who succeeds Martin O'Neill, has agreed a two-and-a-half-year deal.
Di Canio, who led Swindon Town to promotion from League Two last season but resigned in February, has no top-flight managerial experience.
The Black Cats sacked O'Neill on Saturday after a run of poor results left them only one point above the relegation zone with seven games left.
Sunderland chairman Ellis Short said: "Paolo is hugely enthused by the challenge that lies ahead of him. He is passionate, driven and raring to get started.
"The sole focus of everyone for the next seven games will be to ensure we gain enough points to maintain our top-flight status. I think that the chances of that are greatly increased with Paolo joining us."
Di Canio's appointment prompted former foreign secretary David Miliband to resign his post as vice-chairman and non-executive director of Sunderland.
The former Labour Party leadership candidate said: "In the light of the new manager's past political statements, I think it right to step down."
Di Canio has admitted to having fascist leanings, telling Italian news agency ANSA in 2005: "I am a fascist, not a racist."
Speaking half an hour before Di Canio's appointment, former Swindon chairman Jeremy Wray told BBC Radio 5 live: "I think it's a great appointment. He'll galvanise the team. If you're looking for a catalyst for change, he's the right man.
"It's where's he's always wanted to manage and it's a very astute appointment."
The Italian first came to Britain in 1996 when he joined Celtic as a forward, and followed his time in Glasgow with spells at Sheffield Wednesday, West Ham and Charlton.
He retired in 2008 after spells back in Italy with Lazio and former Serie C1 side Cisco Roma, and was handed his first managerial role by Swindon in May 2011, replacing Paul Hart.
Di Canio spent 21 months at the County Ground. After securing promotion, and with Swindon in the League One play-off positions, he quit the Robins on 18 February after becoming frustrated by off-the-field issues.
Recently linked with the managerial vacancy at Reading following Brian McDermott's departure, he told BBC Sport on 13 March that he was ready to manage in the top flight.
He said: "I have already proven my ability in League Two and League One. I believe I am at a stage now where I am a Premier League or Championship manager."
Sunderland are on a run of eight games without a win, with their last league victory coming at Wigan on 19 January.