One of Australia's rarest arid-zone birds, the Princess parrot, has been sighted on the Stuart Highway close to the town of Alice Springs.

The desert dweller has only been seen a handful of times in the last decade in Australia, most recently in a remote part of Newhaven Reserve.

But in an extraordinary sighting, NT Parks ranger Mark Anderson says he saw a small flock just 26 kilometres south of town.

"Driving back from Rainbow Valley, I saw a flock of about six Princess parrots crossing the Stuart Highway," he said.

"It was a flash of green with a lot of pink in there, so I did a big u-turn and went back and followed them.

"Just lucky enough to be in the right place at the right time."