The former Tottenham and Wolves manager returns to a Premier League dugout after two years away, replacing beloved boss Steve Cooper who was sacked on Tuesday.
The 49-year-old, whose last job was in charge of Saudi Pro League champions Al-Ittihad, has penned a two-and-a-half-year contract at the City Ground.
He will take charge of his first match as Reds manager this weekend, for Forest's home clash against Bournemouth on Saturday.
Cooper was initially expected to be in the dugout for that game, with club owner Evangelos Marinakis persistently backing to the under-pressure coach throughout the season.
He is a legend at the club having led Forest back to the Premier League after 23 years outside the top flight, and managed to keep them there last season.
But talkSPORT understands Marinakis felt forced into a change of direction due to the Tricky Trees woeful run of just one win from their last 13 matches.
Forest currently sit 17th in the Premier League table with just three wins all season, and while fans have been unhappy with their recent performances, many voiced their disappointment and upset over Cooper's departure.
Many more have since voiced their displeasure at the impending arrival of Portuguese coach Nuno, who has been sacked from his last two clubs in England and Saudi Arabia.
His appointment with Forest marks Nuno's first job in England since being axed by Tottenham in November 2021, having spent just five months in charge of the north London side.
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After winning the Manager of the Month award for August, enjoying a victory over Man City in his first game in charge, Nuno subsequently lasted just 17 matches in all competitions after taking Spurs from first place to ninth.
He then took his career to the Saudi Pro League, where he took over at Al-Ittihad, leading the club to the title in his first season in charge.
But things began to change in a huge-spending summer, which saw him suddenly become coach to Karim Benzema, N'Golo Kante, Fabinho.
His relationship with star man Benzema began to sour, with the pair eventually falling out and just months after guiding the club to their first title in 14 years, he was was relieved of his duties in November.
His task now at the City Ground is the lift Forest out of relegation danger and consolidate their status as a Premier League club.
He also has a job on his hands to win over their passionate fanbase as the man who replaces the popular Cooper, but may well do it shoujld he turn their fortunes around.