Marshall is Norwich City's fourth signing ahead of their campaign under manager Daniel Farke, joining the likes of Teemu Pukki in the Championship ahead of next season.
The 27-year-old told the official club website: ''It's a good feeling. It's nice to come and see the training ground and meet a few of the lads already so I feel very good.''
''I heard about the interest this summer. When I heard about it, I was very excited and I wanted it to be pushed through. The club is massive. Playing against them for other clubs, obviously the fans are always sold out.''
''I'm really looking forward to training hard. It's nice to get in quite early, previous times I've come in quite late and sort of had to pick up. But I'm glad to be here and can't wait to get cracking.''
Farke is also happy with his newest signing, saying: ''I'm very pleased. We made it clear it's necessary for us to improve the squad. Ben is a pretty experienced player at this level with more than 200 appearances in the Championship.''
''It's good that he is a flexible player. He can play a number of different positions and wherever he played, he showed he was able to be there with some goals and assists.''