The rufous-thighed kite (Harpagus diodon) is a species of bird of prey in subfamily Accipitrinae, the "true" hawks, of family Accipitridae.

[2][3] It is found regularly in Argentina, Bolivia, Brazil, Guyana, Paraguay, and Suriname and as a vagrant in Colombia, French Guiana, and Venezuela.

In the non-breeding season it is regularly found further north in Amazonian Brazil, Bolivia, Guyana, and Suriname.

The SACC also classes the species as hypothetical in Ecuador on the basis of an undocumented sight record.

[7] The rufous-thighed kite is an austral migrant, moving north from its southerly breeding areas into Amazonia.

Its diet appears to be mostly insects such as cicadas and orthoptera with lesser numbers of small lizards, birds, amphibians, and mammals.

It has been observed following army ant swarms and at least once a troop of monkeys to capture prey flushed by them.

[7] The rufous-thighed kite's breeding season is October to February, the austral late spring and summer.