The Chaco eagle (Buteogallus coronatus) or crowned solitary eagle, is an endangered bird of prey from eastern and central South America. Typically it is known simply as the crowned eagle, which leads to potential confusion with the African Stephanoaetus coronatus. Due to its rarity, not much is known about its biology or population.

The Chaco eagle is a large raptor with a mostly dull and silvery grey body plumage. Its short black tail has a broad white medial band as well as a white tip and both its cere and legs are yellow. As its name indicates, the Crowned Solitary Eagle has a crest of darker grey feathers. The juvenile also has a crest but its colour dark brown, except for it creamy head and underbody which are both have grey streaks. It is one of the largest raptors in the Neotropics and normally weighs around 2.95 kg (6.5 lb). Its total length can reach 73–79 cm (29–31 in) and it has a wingspan of 170–183 cm (5 ft 7 in – 6 ft 0 in).

Buteogallus coronatus is monotypic, meaning that there are no subspecies. Vieillot first named it Harpyia coronata in 1817. It was subsequently reclassified by Lafresnaye in 1842 in the genus Harpyphaliatus, as Harpyhaliatus coronatus. At the time, the Solitary eagle (now Buteogallus solitarius) was considered to be a subspecies of Harpyhaliatus coronatus, until phylogenetic analyses of their DNA showed that they are, in fact, sister species. These analyses also indicated that another species, the Great black hawk (Buteogallus anthracinus), is also a sister species. They were all reclassified in the genus Buteogallus.

This bird is endemic to eastern and central South America, where it is present in southern and central Brazil, Bolivia, Paraguay and in Argentina south to northern Patagonia. The status of the Chaco Eagle is uncertain in Uruguay, where it has not been seen for decades and is believed to be extinct. It has become regionally extinct in portions of its historical range, and is found in very low density throughout its range, making it one of the rarest and most threatened raptors in the Neotropical region. Only 250-999 mature individuals are left, while the total individual count of the species reaches 375-1499 birds.

The Chaco Eagle can be found in semi open habitats such as open mixed grasslands, brushlands, savannahs, marshes and open woodlands. Also, the presence of large trees in the habitat is very important for the Chaco eagle since they are used for nesting.

The Chaco Eagle is considered endangered. Its population is declining, a trend that is most likely due to human activities. The Chaco Eagle populations are affected by many threats, including habitat degradation, collisions with human structures, and persecution. An example of the latter would be in Argentina, where Chaco Eagles are still killed due to the belief that they attack livestock. Between 1999 and 2014, 30 Chaco Eagles were brought to a rehabilitation center after they had been shot to protect livestock. For such a small population, this can have a great impact on the species' chances at survival. This persecution attracted the attention of conservation groups, which lead to the creation of a national plan of plan of conservation for the Chaco Eagle in Argentina, the only country to do so so far. Another important factor is the electrocution of Chaco Eagles by power poles, which also has a sizeable impact on their populations. This is also a common problem that unfortunately affects many raptors.

Often seen in solitary pairs or small groups of three, the Chaco Eagle is a tame crepuscular species that forages during early hours.

The Chaco Eagle can be recognized by its very powerful and shrill whistling call that can be heard 2 km away.