In the 2009 season: the Colts and the Saints. First time in NFL history two teams have been 12-0 in the same season.
2009
no
Kansas City Chiefs are currently the only undefeated team as of week 4 at 3-0
The Miami Dolphins. The New England Patriots went undefeated until the superbowl.
1972
No NFL teams went undefeated in 2009.
Colts and Saints.
1972 Miami Dolphins, that is it
Colts and Saints.
Dolphins
There are no more undefeated teams left in the National Football League during the 2010-2011 season
Chicago bears