The Lesser Frigatebird, Fregata ariel, is a species of frigatebird.

It nests in Australia, among other locations.

There is a single record from the Western Palearctic, from Eilat in the Gulf of Aqaba.

The Lesser Frigatebird or Least Frigatebird ('Fregata ariel' is said to be the most common and widespread frigatebird in Australian seas (Lindsey,1986). It is common in tropical seas breeding on remote islands, including Christmas Island in the Indian Ocean in recent years. These birds are most likely to be seen from the mainland prior to the onset of a tropical cyclone, and once this abates they disappear again.

It is the smallest of the three frigatebirds found in Australian waters being about 75cm in length. Like all frigatebirds the male has a large red sac on the front of the throat which is inflated during courtship. Courtship display also involves a variety of calls, bill rattling and spreading of the wings. The male is mostly all black save for a white patch on the flank which extends on to the underwing as a spur. Males also have a pale bar on the upper wing. Females have a black head and neck with a white collar and breast as well as a spur extending on to the underwing. The female also has a narrow red ring around the eye. Juveniles and immature birds are more difficult to differentiate but the presence of the spurs of white in the armpits is a helpful distinguishing sign.

Frigate birds are built for flying; they rarely swim and cannot walk but can manage to climb around the trees and bushes in which they nest. They have a very light skeleton and long narrow wings and are masters of the air. Their name probably derives from the fact that they harass other sea birds such as boobies and tropic birds as they return to their nests from feeding, forcing them to disgorge their catch, which is then swooped upon and caught by the frigare birds before it reaches the water below. This practice seems to be more common amongst female frigate birds, but probably only accounts for a fairly small proportion of the diet, which mainly consists of squid and flying fish scooped up from the surface of the sea.

Breeding seems to occur between May and December in in the Australian region. They nest in trees (on Christmas Island) and both sexes contribute to nest building and incubation and feeding of the young. One egg is laid which takes 6-7 weeks to hatch. Fledglings are not left alone for another seven weeks or so for fear that they may be attacked and eaten by other birds including other frigate birds. They remain in the nest for another 6 months or so until fledged but they are cared for and fed by their parents for quite a long time after that.