There is a lot of information circulating the web about the Jeopardy! theme song, in fact, there is a Wikipedia entry about it. However, I’ll try to keep this as short and as succinct as possible, since we are all probably looking for that one very distinct theme song associated worldwide as the Jeopardy! song.
That song is entitled (or called) “Think!” It was composed by the show’s creator Merv Griffin, which he originall called “A Time for Tony,” as it was a lullaby for his son Tony. It served as the Final Jeopardy! countdown music since the show’s debut in 1964 (hosted by Art Fleming), but, back then, it was not used as the main theme (opening).
“Think!” has been incorporated as the main theme and the Final Jeopardy! countdown music since Alex Trebek took over the show in 1984. It has gone through numerous changes (instrumentation, arrangement) but the basic melody remains. The current version (Jeopardy! 25th Anniversary) was created by Chris Bell Music & Sound Design, Inc.
Additional
Merv Griffin estimated that the Jeopardy! theme song has earned him over $70 million in royalties.
Ken Jennings holds the record of most consecutive games won in Jeopardy! He won 74 in a row with a total of $2,520,700 in prize money.
Listen (current version)