The Jacksonville Jaguars beat the Pittsburgh Steelers and the Minnesota Vikings overcame the New Orleans Saints to sit one win from a Super Bowl spot.
The Jaguars won 45-42 to reach their first American Football Conference championship game in 18 years.
They will now play Super Bowl holders the New England Patriots.
The Minnesota Vikings booked their place in the National Football Conference title game with a 29-24 win and will play the Philadelphia Eagles.
Stefon Diggs made a 61-yard run to touchdown from Case Keenum's throw in the last play of the game for the Vikings in the win over the New Orleans Saints.
Rookie Leonard Fournette was the star for the Jaguars as he ran in three touchdowns and his side will now play the New England Patriots on Sunday, 21 January.
The Vikings will play the Philadelphia Eagles on the same day, with the winners of each game going on to the Super Bowl on Sunday, 4 February.
The Patriots have beaten the Jaguars in seven consecutive meetings and hold a 10-1 winning record against them.
The Eagles last played for an NFC title in the 2008 season and the Vikings in the 2009 season, with both losing.