Forest were reportedly keen to add an option to buy for £20m at the end of the season-long loan, but the deal is nonetheless a huge boost for the Reds.
Henderson joined Man Utd as a 14-year-old and had loan spells at Stockport County, Grimsby Town and Shrewsbury Town before confirming his talent with two seasons at Sheffield United — one promotion from the Championship and a ninth-place Premier League finish with Chris Wilder’s side.
After England appearances throughout his youth, Henderson finally gained a full international cap in 2020 against the Republic of Ireland.
Ole Gunnar Solskjaer at the time said Henderson’s future was as Man Utd’s number one goalkeeper. However, despite 13 appearances during the 2020/21 season he pulled out of Gareth Southgate’s European Championship squad last June with a hip issue and has played little first-team football since.
The 25-year-old will no doubt view this opportunity as a chance to regain both his club and international career.
Steve Cooper said: “Dean is a top-class goalkeeper and he’s hungry for more opportunities to play and to continue to prove himself at the highest level. He’s played multiple times in the Premier League but has also experienced the Champions League and international football.
“Again, Dean is someone who has attracted a lot of interest from other clubs and we’re delighted that he has chosen to Nottingham Forest for our return to the Premier League.”
Henderson added: “I’m absolutely delighted to be joining such a fantastic club with an amazing set of fans and a wonderful history. I want to thank the manager and owners at Nottingham Forest for the great opportunity to play for this club in their first season back in the Premier League. I’m really excited to work with everyone at the club from the manager, players and goalkeeper coach Danny Alcock.
“Finally, just a massive thank you to the fans for the welcome I have received and I can’t wait to celebrate some brilliant moments together this coming season.”
Ethan Horvath has also completed a loan move to Luton Town, while the goalkeeper merry-go-round continues as Brice Samba edges closer to a €5m (£4.3m) move to Lens while Wales international Wayne Hennessey is expected to join the Reds from Burnley.