Kenneth Wayne "Ken" Jennings III (born May 23, 1974) holds the record for the longest winning streak on the U.S. syndicated game show Jeopardy! and, as of October 10, 2008, once again became the all-time leading money winner on American game shows. In 2004, Jennings won 74 Jeopardy! games before he was defeated by challenger Nancy Zerg on his 75th appearance. His total earnings on Jeopardy! are US $3,022,700 ($2,520,700 over his 74 wins, a $2,000 second-place prize in his 75th appearance, and a $500,000 second-place prize in the Jeopardy! Ultimate Tournament of Champions).

During his first run of Jeopardy! appearances, Jennings earned the record for the highest American game show winnings. His total was surpassed by Brad Rutter, who defeated Jennings in the finals of the Jeopardy! Ultimate Tournament of Champions (first aired on May 25, 2005), adding $2,000,000 to Rutter's existing Jeopardy! winnings. Jennings regained the record after appearing on several other game shows, culminating in an appearance on Are You Smarter Than a 5th Grader? (first aired on October 10, 2008), though Rutter retains the Jeopardy! record.

After his success on Jeopardy!, Jennings wrote of his experience and explored American trivia history and culture in Brainiac: Adventures in the Curious, Competitive, Compulsive World of Trivia Buffs, published in 2006. Jennings also appeared as a member of the mob on the game show 1 vs. 100 in 2006, and in 2007 he was the champion of the first season of the US version of Grand Slam.