A planetary reduction gear ring gear for a turbine engine, in particular of an aircraft, the ring gear extending about an axis (X) and including first and second coaxial annular elements and respectively two inner annular teeth oriented differently. The first and second annular elements include respectively first and second radially external annular flanges to secure the first and second elements to one another, the teeth of the first and second annular elements being axially spaced from one another and from a joint plane (P) of the first and second flanges, and defining between them an annular space externally delimited by two annular rims supporting respectively the flanges. At least one of the flanges includes joint plane notches that are substantially radial for the oil to pass through by centrifugation. The ring gear further includes an annular row of oil-retention walls protruding from the rims in the space.