Magnapinna pacifica is a species of bigfin squid known only from three immature specimens; two caught at a depth of less than 300 m (980 ft) and one from a fish stomach.

It is characterised primarily by its proximal tentacles, which are wider than adjacent arms and bear numerous suckers.

The holotype is a juvenile specimen of 51-millimetre (2 in) mantle length (ML), taken off the Californian coast at a depth of 0–200 m (0–660 ft) in a Bongo plankton net.

The paratype (USNM 885787), a juvenile specimen of 49-millimetre (1.9 in) ML, was found in the stomach of a lancetfish (Alepisaurus ferox).

A 2001 observation of an adult long-arm squid off Hawaii by the ROV Tiburon has been assigned to M. pacifica by Vecchione and Young.