Rawson made 73 appearances for Stags during the last two seasons.
“It feels amazing, I am really excited and I am looking forward to the challenges ahead,” Rawson told the Morecambe website.
“I had a really good time at Mansfield, it was a very good learning curve for me, I played a lot of games and got a lot of experience under two different managers.
“Following on from conversations with Greg [Strong] and the manager, about the way they saw, the Club going and the vision they had essentially aligned itself with my own visions and progression.
“The move was a no-brainer for me, their plan is exactly what I want and I want to play my football for a Club that matches that, I can’t wait to get going.
“I have played a lot of games at League Two level and I feel like I have proven myself there to a certain extent, and for me I believe it is time for me to step up a league and test myself again.
“I want to show people what I am capable of, I have done it before and I want to do it again, I want to achieve special things, I want to impress the manager and the fans as well.
“Under this manager I know that I will be able to learn more and add different things to my game, as I said, I have played a lot of games for a 25-year-old, I am a commanding, dominant centre-back that tries to read the game well and I pride myself being bit of a brick wall and getting clean sheets.”