Hutchinson moves to the City Ground for a fee of £37.5m, signing a deal to 2030.
"I'm really excited to be here and can't wait to get started. I've played at the City Ground a few times and it's always felt like a hostile atmosphere, so I'm looking forward to playing here with the fans behind us," said 21-year-old Hutchinson.
"I'm going to give it my all and I'm looking forward to the challenge as it's a new chapter for me, but I feel ready."
Chief Football Officer, Ross Wilson, said: “Omari is a really exciting addition to the squad. He’s coming off a fantastic summer, winning the U21 European Championship alongside Elliot (Anderson), and arrives here full of confidence.
"He joins an already talented group of players and adds another layer of quality and energy to our attacking options. We’re looking forward to seeing him thrive in a Forest shirt.”