The 35-year-old Birk has started every game in three seasons with Baltimore. He briefly contemplated retirement before deciding he wanted to return.
"One of the things we said earlier this offseason is that we were going to focus attention on the offensive line, and getting Matt Birk back is key for us," general manager Ozzie Newsome said. "He is a top player, his intelligence is obvious, and he is a leader on and off the field."
Birk is entering his 15th NFL season.
The former Harvard player left Minnesota as an unrestricted free agent in 2009 to join the Ravens.
Birk has started 96 consecutive games, most among NFL centers.
Copyright 2012 by The Associated Press