Which extinct bird was the largest eagle known to have existed?

The extinct bird recognized as the largest eagle known to have existed was Haast’s eagle.

Haast’s eagle lived on New Zealand’s South Island and disappeared around the fifteenth century. Females are estimated to have weighed roughly 10–18 kilograms, making the species substantially heavier than any living eagle. Its unusual size was an example of island gigantism: in an ecosystem without large mammalian predators, it evolved from much smaller ancestral eagles while exploiting enormous flightless moa as prey.

The eagle’s wings were relatively short and broad for its mass, an adaptation suited to maneuvering through forests rather than soaring across open terrain. It nevertheless remained capable of flight. Its powerful feet, large talons, and robust bill enabled it to attack prey that could weigh up to 200 kilograms.

A common misconception is that Haast’s eagle was itself flightless; the evidence indicates otherwise. Its disappearance followed the loss of moa after human arrival, along with hunting, forest burning, and introduced rats. Māori traditions about the pouākai are sometimes associated with the eagle, though that identification is debated.