The longfin mako shark, Isurus paucus, is a species of mackerel shark in the family Lamnidae, with a probable worldwide distribution in temperate and tropical waters. An uncommon species, it is commonly lumped together under the name "mako" with its better-known relative, the shortfin mako shark (I. oxyrinchus). The longfin mako is a pelagic species found in moderately deep water, having been reported to a depth of 220 m (720 ft). Growing to a maximum length of 4.3 m (14 ft), the slimmer build and long, broad pectoral fins of this shark suggest that it is a slower and less active swimmer than the shortfin mako.

Longfin mako sharks are predators that feed on small schooling bony fishes and cephalopods. It is uncertain whether this shark is capable of elevating its body temperature above that of the surrounding water like the other members of its family, though it possesses the requisite physiological adaptations. Reproduction in this species is ovoviviparous, meaning that the embryos hatch from eggs inside the uterus. In the latter stages of development, the unborn young are fed non-viable eggs by the mother (oophagy). The litter size is typically two but may be as many as eight. The longfin mako is of limited commercial value as its meat and fins are of lower quality than those of other pelagic sharks; it is caught unintentionally in low numbers across its range. The World Conservation Union has assessed this species as Vulnerable due to its rarity, low reproductive rate, and continuing bycatch mortality.