The Geroon were a sentient species originating from a planet located in the Unknown Regions, which shared the epynomous name. In 27 BBY, the Vagaari species captured and enslaved them. Approximately nine Geroons met their death at the hands of B1-Series and droideka battle droids acting under the orders of the Vagaari leader, the Miskara, and a large number were imprisoned in zero-g plastic bubbles attached to the hulls of the Vagaari fleet's vessels. Following their victory over the Vagaari, the Chiss species, via their government, the Chiss Ascendancy, freed them. Admiral Ar'alani of the Ascendancy gave the Geroons foodstuff aboard a transport.
Around 18 BBY, a Geroon encountered Sele, a Cathar, and in 22 ABY, several Vagaari, including Supreme Commander Estosh, General Bearsh, and Purpsh, disguised themselves as Geroons to infiltrate the Chiss expedition heading to the remnants of the Outbound Flight colony starship. While many members of the expedition remained unaware of the deception, Aristocra Formbi of the Ascendancy was aware and permitted them to join his group in order to initiate a war against the slavers. Ultimately, Mara Jade, a Jedi Knight, and Luke Skywalker, a Jedi Master, defeated the Vagaari.
The Geroon were initially referenced in Timothy Zahn's 2004 novel, Survivor's Quest, and subsequently featured in Zahn's 2006 novel, Outbound Flight.