The black swallower (Chiasmodon niger) is a species of deep sea fish in the family Chiasmodontidae.

It has a worldwide distribution in tropical and subtropical waters, in the mesopelagic and bathypelagic zones at a depth of 700–2,745 m (2,297–9,006 ft).

With its greatly distensible stomach, it is capable of swallowing prey over twice its length and 10 times its mass.

[7][8] In 2007, a black swallower measuring 19 cm (7.5 in) long was found dead off of Grand Cayman.

Its stomach contained a snake mackerel (Gempylus serpens) 86 cm (34 in) long, or four and a half times its own length.

[9] Reproduction is oviparous; the eggs are pelagic and measure 1.1–1.3 mm (0.043–0.051 in) in diameter and contain a clear oil globule and six dark pigment patches, which become distributed along the newly hatched larva from in front of the eyes to the tip of the notochord.