The 23-year-old winger put pen-to-paper on a three-and-a-half year deal after joining from fellow promotion hopefuls Swindon on Wednesday and says he is joining a club that is on the up.
"I'm very happy to be here and I think it's a great project," Ritchie, who was named League Two player of the year last season, told the club's official website. "The club is going places.
"The run that the team has been on for the last couple of months has been phenomenal and hopefully we can continue that through to the end of the season and get promoted.
"I believe this club can get into the Championship and that is why I've come here.
"There's a good manager here and the amount of quality throughout the squad is unbelievable for this league. If I am honest I can't see the club staying in this league for long."
Manager Eddie Howe believes the addition of the winger sends out a clear message to the rest of League One.
"I think it sends out a statement of our ambition and what we are trying to create here," he told the club's official website. "It's a big signing for us.
"I have known him a number of years and I have always admired him as a footballer and as a person, so I think it's a really good signing not just for now but for the future as well.
"Matt's a great lad, he's determined to succeed, he's got real determination to play at the highest level possible and hopefully he can do this with us."
- Sports & Recreation