The abyssal halosaur (Halosauropsis macrochir) is a species of bottom-dwelling, deep-sea fish in the family Halosauridae that is found in all oceans at depths of 1100 to 3500 meters.

[3] Abyssal halosaur can reach total length of at least 76 centimetres (30 in) and weight in excess of 400 grams (14 oz).

Berstad et al.[2] could not sex fish smaller than 25 cm, giving an indication about length at maturation.

Abyssal halosaur are long-lived, with maximum reported age of 36 years, although individuals sampled on the Mid-Atlantic Ridge were mostly <20 years.

It appears to be an opportunistic feeder, mostly taking epibenthos and small fish.