Martin thanked the 49ers via Twitter and said he's looking forward to playing for another team.
He spent one season in San Francisco, appearing in 15 games (nine starts) at right tackle.
Martin played at Stanford and was a 2012 second-round draft pick by the Miami Dolphins. He started all 16 games as a rookie.
In Martin's second season with Miami, he left the team in October 2013 after a bullying controversy involving former teammate Richie Incognito. An NFL investigation determined Incognito and two other Dolphins offensive linemen engaged in persistent harassment of Martin.
Martin played the first seven games but sat out the rest of the 2013 season, and then in the offseason the Dolphins traded him to the 49ers for a conditional seventh-round draft pick.
Information from The Associated Press was used in this report.