Rilaena triangularis is a harvestman that lives across Europe.

This species was first described by Johann Friedrich Wilhelm Herbst in 1799, initially as Phalangium triangularis.

[2] When disturbed, Rilaena triangularis emits a strong-smelling secretion as a chemical defense.

Occurrences of Rilaena triangularis have been recorded and aggregated in GBIF across Europe, with the exception of Spain and Portugal.

It has also been observed in north-west and north-east corners of the United States.