The team made an announcement late Tuesday.
Fangio interviewed with the Bears on Saturday, and he met Sunday with the Washington Redskins for a second interview. The Redskins ended up settling on Joe Barry as their defensive coordinator Tuesday.
Fangio had been released from his contract with the San Francisco 49ers after the team promoted Jim Tomsula to head coach. Fangio had hoped to land the 49ers' head coaching job, and reportedly made his intentions known he did not want to stay in any other capacity.
During Fangio's last four years as defensive coordinator of the 49ers, the club ranked in the top 10 in points and yards. In Fangio's first three seasons in San Francisco (2011-13), the 49ers were the only team in the NFL to finish in the top five in points allowed (16.1 points per game), run defense (89.1-yard average), rushing average (3.7), first downs allowed (835), opponent quarterback rating (76), yards allowed (306.5 yards per game), plays for gains of 20-plus yards (147), takeaways (93) and third-down defense (34.1 percent conversion rate).
San Francisco's defense in 2014 was hit hard by injuries, but Fangio led the unit to a No. 5 overall ranking as the defense ranked No. 10 in the league in points allowed (21.2 points per game).
Fangio, 56, joins the Bears with 28 years of NFL coaching experience, including 15 as a coordinator. He takes over for Mel Tucker, who presided over a Bears defense that ranked 30th overall in each of the past two seasons and 31st in 2014 and 30th in 2013 in points allowed.
The hiring caught the attention of offensive lineman Kyle Long, who tweeted out his approval.
DC Fangio Joins Bears Coaching Staff
Marty Hurney discusses why Vic Fangio was the right choice to be the Bears' defensive coordinator.