The Jeopardy! Battle of the Decades is a special 5-week tournament airing throughout the 30th season of the syndicated game show Jeopardy! to commemorate the 30th anniversary the Alex Trebek-version of the show. The tournament involves 45 previously successful Jeopardy! contestants split into three groups based on the time period of their initial appearance on the program. Though the groups actually represent 1984-1993, 1994-2003, and 2004-2013, they are referred to as the 1980s, 1990s, and 2000s, respectively. The tournament's 1980s round began airing on February 3rd, 2014 with the tournament's final episode set to air later that year on May 16th, covering 25 shows in total. The tournament's grand prize is slated to be US$1,000,000.

45 contestants participated in the Battle of the Decades, with 15 players from each "decade" the Trebek-version on Jeopardy! had been airing. Of the 45 participants, three were selected by the viewers using an online Twitter poll, with the choices coming from a producer-created shortlist of 15 possible players.

The tournament was played in four separate rounds. The first three rounds featured contestants grouped by year of their initial appearance on the show, and competing against players from the same "decade" (as defined by the program). Gameplay in this round was of the sudden death variety, with only the winner of each game moving on to the final round of the tournament.

The tournament's final round will consist of the traditional two-week tournament format, with a week of quarterfinal matches between the 15 players passing through their decade's round. These matches will produce 9 semifinalists, consisting of the the five quarterfinal winners and four wild cards. The winners of each semi-final game will compete in a two-day, cumulative championship match for the grand prize of $1,000,000.

Contestants in the 1980s bracket of the tournament initially appeared on Jeopardy! from 1984-1993.