|Crew:||At least 16|
|CO:||Kara Thrace (detached)|
|XO:||Karl Agathon (detached)|
|Aircraft:||Detachment of five Vipers and a Raptor from battlestar Galactica|
|Fate:||Scuttled, circa YR04 (4 years ACH)|
Demetrius is a sewage processing ship in the Fleet. Circa YR04, it is requisitioned for military use by Admiral William Adama following the return of Cpt. Kara Thrace for a mission to locate Earth (TRS: "Six of One"), however, the surviving Colonial public are told that they are on a survey mission to find food sources, though its disappearance is a matter of considerable media attention (TRS: "The Ties That Bind"). Demetrius is scheduled to rendezvous with the Fleet after two months or be presumed destroyed. Demetrius is accompanied by a detachment of five Vipers that are magnetically secured to the ship, and a Raptor that is secured to a docking hatch on either side of the vessel.
After encountering a Heavy Raider with a copy of Leoben Conoy aboard, however, Thrace decides to abandon the plan to return to the fleet. Conoy offers an alliance between the humans and his faction in the Cylon civil war, and Thrace wants to accompany him to his baseship in order to learn what the Cylons know about Earth, but her crew refuses to carry out the order (TRS: "The Road Less Traveled"). Eventually, the Raptor is launched to the basestar, while the ship remains in its current location. After the baseship is cleared, both it and Demetrius sync their FTL drives to return to the fleet simultaneously, however, a malfunction in Demetrius's FTL drive causes the baseship to jump to the fleet alone. It ends up in the middle of the Colonial Fleet causing civilian vessels, along with Galactica, to scramble before Demetrius jumps in to defuse the situation (TRS: "Guess What's Coming To Dinner"). Following its return to the fleet, control of the ship is immediately returned to the previous owners.
Demetrius is ultimately scuttled following the settlement of a habitable planet the Colonials find following the Battle of the Colony. It is flown into the planet's star along with the other remaining fleet ships (TRS: Daybreak, Part II").
The main quarters area of the ship are small and cramped like that of a submarine. Even the captain's cabin is small and sparse. A common area exists for the crew to assemble and eat their meals.
The ship's bridge is laid out like a small CIC with a table in the center, surrounded by various screens and a tactical plot.
Demetrius's crew consists of:
- Kara Thrace - Commanding Officer
- Karl Agathon - Executive Officer
- Felix Gaeta - Navigator / Watch Officer
- Sharon Agathon - Raptor pilot
- Samuel Anders - Viper pilot
- Diana Seelix - Viper pilot, bridge staff
- Brendan Costanza - Viper pilot, bridge staff
- Eammon Pike - Viper pilot
- Unnamed tattooed pilot - Viper and Raptor pilot
- Erin Mathias† - Marine detachment commander
- Jean Barolay† - Civilian volunteer
- At least two additional unnamed Marines
- At least three other unnamed crew members
- The ship's name is first shown on the voting tally board in "Lay Down Your Burdens, Part II", but it doesn't appear until the Season 4 episode "The Ties That Bind".
- Ron D. Moore describes the ship as the "closest we’ve ever come to a sort of Das Boot – type look and feel on this program since the  Miniseries".
- Demetrius was the name of several Hellenistic rulers, most notably in the Seleucid and Indo-Greek kingdoms. The name is derived from the goddess Demeter.
- Demeter is the Greek goddess of grain and agriculture, the pure nourisher of youth and the green earth, the health-giving cycle of life and death, and preserver of marriage and the sacred law.
- Cullen, Ian M. (11 December 2007). Ron Moore Gives Some Further Insights Into Season 4 Of Battlestar (backup available on Archive.org) (in ). Retrieved on 14 December 2007.