Varanus gilleni, a species of lizard in the family Varanidae. Named after F.J. Gillen, chief officer of the Alice Springs telegraph station in 1894. These lizards were said to warn of the presence of crocodiles, and became known in English as monitors. They generally live under the exfoliating bark of Mulga trees.

The pygmy mulga monitor is arboreal, with a prehensile tail. It grows to a total length of around 30–40cm. The upper surface is brown, grading to grey at the sides. The nostrils are positioned on the sides of the muzzle, about halfway between the tip of the snout and the eye. They weigh on average 60–80 grams.