Seljin Gandres was an unjoined male Trill, with long brown hair and brown eyes and the Trill ambassador to the United Federation of Planets in the 2370s. Gandres knew Admiral Leonard James Akaar well enough to greet him as L.J.

In June 2376, Ambassador Gandres and his aide, Hiziki Gard, visited Deep Space 9 and Bajor as part of the Federation delegation to assess Bajor's admittance into the United Federation of Planets. Once at the station, Gandres asked Colonel Kira Nerys if he could meet with the Jem'Hadar Taran'atar on behalf of the Federation Council. (DS9 - Mission Gamma novel: Twilight)

After Gard assassinated Shakaar Edon, Ambassador Gandres turned over the Trill response to the crisis to General Taulin Cyl. (DS9 novel: Unity)

Ambassador Gandres liked Ferengi foods, like tube grubs. (DS9 - Mission Gamma novel: This Gray Spirit)