海龙（学名：Thalattosaurus）是种已灭绝海生爬行动物，属于海龙目，生存于三叠纪。海龙的身长约2公尺，被推测以贝类为食。

海龙目前已发现两个种：模式种T. alexandrae、以及1993年发现于加拿大卑诗省的北方海龙（T. borealis）。

Thalattosaurus (pron.:"tha-la-to-SORE-us") meaning "ocean lizard" is an extinct genus of marine reptile in the family Thalattosauridae. They are aquatic diapsids that are known exclusively from the Triassic period, and have recently gained attention as a result of studies on general diapsid phylogeny.