A new strigeid digenean, Parastrigea macrobursa n. sp., is described from specimens recovered from the small intestine of the great black-hawk, Buteogallus urubitinga (Aves: Accipitridae), from Formosa Province, Argentina. The new species is characterized by having a tulip-shaped forebody, a hindbody without neck region, a large, well delimited copulatory bursa, and a very deep genital atrium. Three species of Parastrigea share the shape of the copulatory bursa namely P. faini, P. astridae and P. tulipoides. Parastrigea faini and P. astridae differ mainly from the new species by having the forebody strongly divided in two regions and very developed lateral expansions, and Parastrigea tulipoides by having a long neck region and a longer body size. This new species represents the first record of a member of the genus Parastrigea Szidat, 1928 parasitizing birds from Argentina. A key is presented for the species currently recognized as valid in the genus.