Timorebestia koprii is an extinct species of stem-group chaetognath (arrow worm relative) that lived about 520 million years ago, in the Cambrian.

The anterior region is a short head, bearing a pair of antennae as long as half of the body length.

It also has a pair of well-defined ventral ganglia that identifies it as a chaetognath, but was probably more basal to modern arrow worms than Amiskwia.

It lived alongside other nektonic Sirius Passet fauna such as Kerygmachela, Kiisortoqia, Pauloterminus, Isoxys and so on.

The species name is derived from the Korea Polar Research Institute (KOPRI), who has helped with the expeditions to the lagerstätte.