A dark matter proto-comet is a theoretical type of comet made up of dark matter.

Crewman Mortimer Harren of the USS Voyager once wrote a paper on dark matter proto-comets. He theorized that a tertiary byproduct of stellar consolidation would be a comet-like assemblage of dark matter. It would be attracted to any source of antimatter and then neutralize it upon impact. He thought that the Delta Flyer was struck by a dark matter proto-comet in 2376 when the ship was impacted by an unknown phenomenon. However, it was discovered that the ship was actually struck by a dark matter lifeform. Therefore the existence of such a comet still remains only a theory. (VOY: "Good Shepherd")