Brian Wilson has left Colchester to become Oldham's third summer signing on a two-year deal.
The 31-year-old was captain of the U's and had been offered a new contract but the defender was keen to return to his native north west.
Wilson told Colchester's official website: "I thoroughly enjoyed my time at the U's, I wanted to stay but we couldn't agree terms.
"There were a great bunch of lads and I wish them and the club all the best for the future."
Wilson played with Latics boss Lee Johnson at Bristol City .