Although it officially dates back to November 1970, the rivalry between the Cincinnati Bengals and Pittsburgh Steelers took a few explosive turns in 2015, contributing to perhaps the most hate-filled series in professional football.
If there was any doubt about the hatred these teams had for one another, that faded after three intense meetings.
Penalties, pregame scuffles, postgame tweets and a playoff meeting defined the games between the longtime foes.
With both teams' seasons now over, we look back at four ways their rivalry impacted the 2015 season:
More key late-season injuries.