Bradley has spent the last four seasons as the defensive coordinator for the Seattle Seahawks.
General manager David Caldwell said in a statement: "It was just a matter of time before Gus Bradley became a head coach in the NFL and the Jacksonville Jaguars are extremely fortunate that Gus will be on our sidelines for many years to come.
"Gus more than met every criteria we insisted on from our new head coach, and his intangibles and leadership abilities are exceptional. Gus is who the Jaguars need now and in the future."
Mike Mularkey was fired by the Jags last week, having led the side to only two wins during 2012.