The 53-year-old Scot will begin work at the City Ground tomorrow and it is confirmed he will take charge of Forest's game on Saturday against high-flying Crystal Palace
After the suprise departure of Sean O'Driscoll following Forest's 4-2 win over Leeds on Saturday, the club have moved swiftly to appoint the former Aston Villa, Birmingham City and Scotland manager, despite speculation linking the club with Roy Keane and Roberto Di Matteo.
Chairman Fawaz Al-Hasawi hailed the appointment, revealing himself to be "delighted" to welcome McLeish to the City Ground.
“I’m delighted to welcome Alex to our club and look forward to working with him," the Forest owner told the club's official website.
“Alex took Birmingham to promotion from the Championship and has great experience of working in the Premier League.
“He’s hungry for more success and I believe he’s the man who can help us fulfil our ambition of making it to the Premier League.”
McLeish made his name at Rangers, winning seven of his eight managerial trophies at the Glasgow club.
His last trophy was won during his time with Birmingham City, leading them to a historic League Cup victory against Arsenal in 2011.