Onilahy (or Ionilahy) is a rural municipality in Madagascar.

It belongs to the Manakara-Atsimo District, which is a part of Fitovinany.

Farming and raising livestock provides employment for 40% and 40% of the working population.

Industry and services provide employment for 19.7% and 0.3% of the population, respectively.

[1] Ionilahy is a station on the Fianarantsoa-Côte Est railway.