Atelopus nahumae (San Lorenzo harlequin frog) is a species of toad in the family Bufonidae.

It is endemic to Colombia and only known from humid montane forest of Sierra Nevada de Santa Marta in the Magdalena, La Guajira, and Cesar Departments.

[2] Atelopus nahumae inhabits sub-Andean forests at elevations of 1,900–2,800 m (6,200–9,200 ft) above sea level.

It is potentially threatened by chytridiomycosis (although as of 2014, the disease has not been detected in Sierra Nevada de Santa Marta) and by habitat loss caused by agriculture and logging.

The species occurs within the Parque Nacional Natural Sierra Nevada de Santa Marta as well as the adjacent El Dorado Nature Reserve.