Williams' agent, Bob Myers, told ESPN.com that the 32-year-old -- who spent the past three seasons with the Miami Heat and who started at point guard for Miami's title-winning team in 2006 -- has signed with the Clippers.
Financial terms were not immediately available, but NBA front-office sources said Williams is receiving a one-year contract.
"We are excited to add Jason to our squad," Clippers coach Mike Dunleavy said in a statement. "He brings added veteran leadership and playoff experience to our backcourt."
In 679 regular-season games, Williams has averaged 11.4 points, 6.3 assists and 2.4 rebounds while playing for three different teams. He has appeared in 53 playoff games, averaging 9.8 points, 3.7 assists and 2.2 rebounds.
Clippers general manager Elgin Baylor called Williams "a terrific ball handler with great passing ability and court vision."
Williams ranked eighth in the league last season with a 3.37 assists-per-turnover ratio, and 12th with a 0.91 steals-per-turnover ratio.
He was drafted by Sacramento in 1998 following his junior year at the University of Florida and was named to the 1999 NBA All-Rookie Team after he averaged 12.8 points and 6.0 assists. He has averaged scoring in double figures and at least five assists a game in eight of his 10 years in the league.
Williams moved to Memphis before the 2001-02 season and over the following four years became the Grizzlies' career leader in assists and 3-point attempts. He joined the Heat before the 2005-06 season.
Williams will thus become the 10th new player acquired by the Clippers in the wake of a disastrous 23-59 season, which was followed by Elton Brand's free-agent defection to the Philadelphia 76ers.
Los Angeles native Baron Davis headlines the group of newcomers, which also includes center Marcus Camby, Williams' former Miami teammate Ricky Davis, first-round draft pick Eric Gordon, veteran forward Brian Skinner and sharpshooter Steve Novak, whom L.A. landed Wednesday in a trade with the Houston Rockets.
The addition of Williams -- who recently attracted serious interest from Israeli giant Maccabi Tel-Aviv before Maccabi signed Orlando Magic free agent Carlos Arroyo -- all but ensures that the Clippers will not re-sign point guard Shaun Livingston. L.A. renounced its free-agent rights to the injury-plagued Livingston on July 9 to help create the requisite salary-cap space to officially sign Davis to his five-year, $65 million contract, but the Clippers did have the option of trying to re-sign him.
Marc Stein is the senior NBA writer for ESPN.com. To e-mail him, click here. Information from The Associated Press was used in this report.