Smith retires after 14 seasons, seven of which were spent with the Cincinnati Bengals and seven with the 49ers. The Bengals selected him with the No. 4 pick in the 2001 draft after four years at Missouri.
The 35-year-old signed a six-year deal with San Francisco in 2008 and went on to be named to five straight Pro Bowls from 2009 to 2013. In 2011, he was named the Sports Illustrated Defensive Player of the Year.
Smith started all 16 games for the 49ers last season, making 43 tackles and 5.0 sacks. In his career, he recorded 880 tackles and 87.0 sacks in 217 starts. He played in all but three of a possible 224 regular season games over his 14 years.
In March, San Francisco linebacker Patrick Willis announced his own retirement. Later that month, 49ers linebacker Chris Borland retired at age 24 due to concerns about the long-term effects of repetitive head trauma.
In all, Smith is the seventh departure from San Francisco's defense this off-season. The 49ers defense was ranked No. 10 in points allowed and No. 5 in yards per game in 2014.
- Molly Geary