| Named By: | Florentino Ameghino in 1887 |
| Time Period: | Miocene, 20-13 Ma |
| Location: | Argentina, Santa Cruz Province |
| Size: | 2.5 meters tall, Skull up to 60 centimetres long |
| Diet: | Carnivore |
| Fossil(s): | Many known specimens |
| Classification: | | Chordata | Aves | Cariamae | Phorusrhacidae | Phorusrhacinae | |
| Also known as: | | Callornis giganteus | Darwinornis copei | Darwinornis socialis | Darwinornis zittelli | Eucallornis giganteus | Liornis floweri | Liornis minor | Mesembriornis quatrefragesi | Mesembriornis studeri | Owenornis affinis | Owenornis lydekkeri | Phororhacos longissimus P. platygnathus | Phororhacos sehuensis | Stereornis gaundryi | Stereornis rollieri | Titanornis mirabilis | |
Phorusrhacos longissimus (pronounced FOR-rus-RAH-kos) is an extinct, giant flightless predatory bird that lived in Miocene Patagonia. P. longissimus' closest living relatives are the much smaller seriemas. P. longissimus is thought to have lived in woodlands and grasslands.
Phorusrhacos grew up to 2.5 metres (8.2 ft) tall and weighed approximately 130 kilograms (290 lb). They had enormous skulls up to sixty centimetres (24 in) long, armed with powerful, hook-tipped beaks. The structure of the beak and the large claws on the toes show that they were carnivorous.