The Secret Treasure of the Jedi was a rumored treasure hidden by the Jedi within the Jedi Temple's basement. Despite its vast value, it was contained within a small, handheld box.
Palpatine used the rumor of this treasure to lure Vilmarh Grahrk into helping him with the Yinchorri Uprising. Palpatine may have stolen it during the Yinchorri attack on the Temple. Anakin Skywalker also had heard rumors of large amounts of treasure being hidden in the Temple.
While accompanying Ferus Olin in breaking into the Jedi Temple Trever Flume was another who believed that the treasure indeed existed; however Ferus dismissed the rumor as propaganda.