In Star Trek, a subspace sinkhole is a unidirectional anomaly that produces an extremely strong gravity well, drawing matter into it whenever it opens. Sinkholes are dangerous to starships because the gravimetric shear it emits disrupts the formation of warp fields, preventing escape. When inactive, subspace sinkholes are out of phase with normal space-time, making them difficult to detect.

In 2375, the USS Voyager was almost pulled in by a subspace sinkhole in the Delta Quadrant, which had already swallowed one of its shuttlecraft. The anomaly measured 600 meters in diameter and led to a subspace pocket containing a G-type star with three planets. The pocket experienced a temporal differential, such as that 1.4744 seconds passed on the outside for every minute inside.

The shuttle, carrying Tuvok, Tom Paris, and the Doctor, had crashed on one of the planets. Using their multispatial probe as a relay, the Voyager crew was able to transport their people out, along with their friend Noss. Shortly after, the sinkhole was collapsed by Renovation Team Nova, destroying the system within. (VOY: "Gravity").

The closest equivalent to subspace sinkhole in astrophysics appear to be black holes and and they may in fact be subspace equivalents of black holes in normal space. Black holes also demonstrate the characteristics of a subspace sinkhole, including a strong gravity well and possible temporal effects as the spacetime continuum is distorted and warped towards the centre.