The Bigeye thresher, Alopias superciliosus, is a thresher shark of the genus Alopias, found in tropical oceans worldwide, at depths down to 1640.42 ft (500 m). Its length is up to 16.4 ft (5 m) and weight up to 793.66 lbs (360 kg).
The Bigeye thresher is a large shark, with very large eyes indicating time spent at unlit depths. It has an indented forehead and large broad pectoral fins, and the first dorsal fin set further back than that of other thresher sharks. The upper caudal lobe is very long and strap-like, virtually the same length as the body.
The color is purplish grey above, bream below, with posterior edges of pectoral and pelvic fins dusky.