Williams, 30, joins Brandon Meriweather as the second free agent safety acquired by Washington this offseason. The Redskins are in need of help at the position after releasing both LaRon Landry and Oshiomogho Atogwe this spring.
The San Francisco 49ers let Williams go after signing him as a free agent prior to the 2011 season. He started just three games as a backup last season. Prior to that, Williams was a regular starter in his final two seasons with the Minnesota Vikings. Williams was the Cincinnati Bengals' second-round pick in 2004; he spent four seasons there, before joining the Vikings.