Leptothyra is a genus of sea snails, marine gastropod mollusks in the family Colloniidae.

Although Leptothyra is a junior objective synonym of Homalopoma, the species usually treated as valid in that genus are provisionally listed in WoRMS under "Leptothyra sensu Pease, 1869", pending a taxonomic/nomenclatural reappraisal.

[2] Leptothyra J. G. Cooper, 1867 is now considered a junior objective synonym of the genus Homalopoma Carpenter, 1864.

[3] The small, solid shell has a turbinate or globose shape.

The main character distinguishing Collonia from Leptothyra seems to be the peculiar peristome of the former.