Hydrophis fasciatus, commonly known as the striped sea snake, is a species of venomous sea snake in the family Elapidae (Hydrophiinae).
Hydrophis fasciatus has a small head, long body and is slender anteriorly. The scales on thickest part of body are subquadrangular or hexagonal in shape, juxtaposed or slightly imbricate. It has 5-6 maxillary (upper jaw bone) teeth behind fangs and 2 anterior temporals.
Body scales in 28-33 rows around the neck, 47-58 around midbody (increase in number of rows from neck to midbody 20–27); ventral scales 414-514 (average 460).
Anterior part of body including head and neck dark olive to black with pale oval yellowish spots on sides, sometimes connected as crossbars; posterior, grayish; below whitish; dark rhomboidal spots may extend down the sides of the body and form complete annuli in young.
Total length males 1100 mm, females 990 mm; tail length males 100 mm, females 75 mm.