The Raiders originally signed Penn in 2014 after the Tampa Bay Buccaneers allowed him to leave in free agency. He spent five seasons with Oakland.
"Thank you to [owner] Mark Davis and the entire Oakland Raiders organization for giving me an opportunity to play for you," Penn said. "It was an honor to play for you. Thank you to my Raiders teammates for always going to war and leaving it all on the field. It was an honor to play beside you.
"To Coach [Jon] Gruden -- thank you for always believing in me. From giving me my first start back in Tampa, it's incredible how things come full circle. I appreciate everything you've done for me."
Penn started each of his 66 appearances with the Raiders, including all 16 regular-season games in his first three seasons with the team.
Last season, Penn started four games before Oakland placed him on the reserve/injured list with a groin injury Oct. 3. Before his injury, he had his role changed with the team. Raiders head coach Jon Gruden shifted Penn to right tackle and put 2018 first-round pick Kolton Miller at left tackle.
"We're going to miss Donald Penn around here," Gruden said. "I got to coach him as a young guy in Tampa and everything he got on the field, he earned. I was lucky enough to get him again here in Oakland. I'm going to miss the toughness and passion that he brought to the team every day. I certainly wish him and his family all the best."
Penn is a three-time Pro Bowl Selection (2010, 2016, 2017). Over his 13-year NFL career, he has appeared in 178 games and made 174 starts.
Penn entered the league as an undrafted free agent in 2006 with the Minnesota Vikings. The Vikings released him, and the veteran lineman joined the Buccaneers, where he spent eight seasons (2006-13).