Season 21 (2004-2005)
- The opening credits have changed to the Jeopardy! logo in gold, which is superimposed over a colorful background.
- The "DAILY DOUBLE" name and the "DOUBLE" and "FINAL" in Double and Final Jeopardy! again use Impact, as do the words "VIDEO" and "AUDIO" in Video and Audio Daily Doubles; the "DAILY DOUBLE" name now appears in silver, while all the rest remain red.
- The contestant intros and Final Jeopardy! winnings changed its color to slate purple strips with white borders and white, italicized, shadowed text in Compacta-D. Starting on December 27, 2004, the color of the strips changed to blue.
- For this season and the next, the category names are switched to Haettenschweiler.
- This is the final season in which there is no saxophone and electric guitar riffs used during the end credits.
- Season 21 of Jeopardy! kicks off on September 6, 2004.
- This season would be the last to kick off on Labor Day.
- The Tournament of Champions was held from September 20-October 1, 2004.
- Until Season 29, this tournament was the last time where the champions in the quarterfinals week were in the order of how much money they have won in their initial appearances.
- Ken Jennings' 49th through 73rd games do not mention the number of days he was champion, due to the date of his final episode being leaked.
- Starting with the October 4, 2004 episode, the logo is more golden and less reflective.
- The October 8, 2004 episode is the well-known incident of Ken Jennings' viral response of "What is a hoe?"
- On the October 18-22, 2004 episodes, Back to School Week is held.
- On the October 25, 2004, Ken Jennings becomes the first contestant to break the $2,000,000 mark.
- The November 2-5, 2004 episodes are pushed one day later to November 3-6, 2004 due to the 2004 Presidential Election being held on November 2, 2004.
- On November 3, 2004, Ken Jennings had broken Kevin Olmstead's record for biggest amount of money won on a television game show.
- The College Championship was held at the University of Pittsburgh and aired from November 10-24, 2004.
- On the November 30, 2004 episode, Ken Jennings' winning streak comes to an end with a 74-day total of $2,520,700. He is beaten by Nancy Zerg, who loses the next day.
- On the December 1, 2004 episode, Ken Jennings is brought out at the beginning of the show to be recognized for his place in game show history.
- The Teen Tournament is held from January 26-February 8, 2005, with winner Michael Braun becoming the last qualifier for the Ultimate Tournament of Champions.
- The Ultimate Tournament of Champions is held from February 9-May 25, 2005. Ken Jennings, Jerome Vered, and Brad Rutter face off in the finals.
- On the February 23, 2005 episode, this is only the third episode in the game show's syndicated history where only one contestant plays Final Jeopardy!.
- Rutter wins the tournament with a $2,000,000 cash prize, making him the biggest game show money winner at the time, as of today, he is no longer the biggest money winner of all time, as Ken Jennings took the title in 2020 with his victory in the Greatest of All Time tournament. He still holds the record for most money won on Jeopardy!
- David Madden makes his Jeopardy! debut on the July 5, 2005 episode.
- Season 21 of Jeopardy! wraps up on July 22, 2005. It also marks the last episode that electric guitar riffs and saxophones aren't used in the credits.
- Summer reruns air from July 25-September 9, 2005, with replacement fee plugs. The summer reruns include some of the Ultimate Tournament of Champions. Reruns later air on weekends from 2005-2006. Eventually, reruns air on Game Show Network under the GSN branding in the late 2000s, including the entire Ultimate Tournament of Champions.