Phalotris is a genus of snakes of the subfamily Dipsadinae. All species of the genus Phalotris are found in South America. The specific name, mertensi, is in honor of German herpetologist Robert Mertens. The specific name, normanscotti, is in honor of Norman Scott, Jr., in recognition of his contribution to the knowledge of the herpetofauna of Paraguay.

Dipsadinae is a large subfamily of colubroid snakes, sometimes referred to as a family (Dipsadidae). Species of the subfamily Dipsadinae are found in most of the Americas, including the West Indies, and are most diverse in South America. There are more than 700 member species.