Kilmarnock have appointed Derek McInnes as manager on an 18-month deal.
McInnes has been out of work since being sacked by Aberdeen last March after a disappointing run of results.
The 50-year-old former St Johnstone manager will replace Tommy Wright, who was sacked after the Ayrshire club's promotion bid faltered with four defeats in five matches.
Killie - who were relegated last season - are sitting fourth in the Championship, five points behind surprise leaders Arbroath with a game in hand.
McInnes will be joined at Rugby Park by long-term assistant Tony Docherty and his first game in charge will be against Queen of the South at Palmerston Park on Saturday.
He told Sky Sports News: "I don't want to be in the Championship anymore than Kilmarnock want to be but we find ourselves here as a club.
"We need to try and get back up as quickly as possible. There is an expectation and pressure to get the club back as quickly as possible.
"It is up to me now to use this month of January to make the necessary improvements and get a winning team on the pitch that allows us to enjoy the last game of the season, going up as champions.
"That is the intention but it is an easy thing to say. Just because we are a big club, that gives you no guarantees. We need to work harder than everybody else and hopefully have a strong end to the season."
After leading St Johnstone to promotion to the top flight in 2009, McInnes had a spell at Bristol City before taking charge of Aberdeen in 2013.
He led the club to their first piece of silverware in two decades the following year when they beat Inverness to win the Scottish League Cup and also steered the club to four second-place finishes.
Wright oversaw a major squad rebuild at Rugby Park last summer, but was dismissed after just 10 months in charge.