Pachystruthio is an extinct genus of large flightless birds which lived in Eurasia from the Pliocene to the Middle Pleistocene. Its fossils have been found in Hungary, Greece, Crimea, Georgia, and China. Pachystruthio was related to living ostriches, being a sister group of the genus Struthio, the genus of living and extinct species of ostriches. One of the species, P. dmanisensis, has been estimated as standing 3.5 metres (11 ft) tall and weighing around 450 kg (990 lb), making it much larger than the modern ostrich and one of the largest known birds.