Parablechnum cordatum (synonyms Blechnum cordatum, Blechnum chilense), the Chilean hard fern or costilla de vaca (Chilean Spanish for "cow´s rib"), is a fern of the family Blechnaceae, native to Chile. It is also found in neighboring areas of Argentina and the Juan Fernández Islands.

It grows to , often developing a trunk-like appearance over time. The fertile fronds are more erect, with narrower pinnae, than the infertile ones.

This plant has gained the Royal Horticultural Society´s Award of Garden Merit.