Tyrannomolpus is a genus of leaf beetles in the subfamily Eumolpinae. It is known only from Three Kings Islands, New Zealand. It contains only one species, Tyrannomolpus rex. T. rex is the largest chrysomelid beetle species endemic to New Zealand, measuring between 9.7 and 11.9 mm, and may be an example of island gigantism. It has a dark bronzy-green color with a metallic luster. Tyrannomolpus is closest to the genus from the mainland of New Zealand. A single specimen of the species was collected from Meryta sinclairii (also known as the puka), a tree endemic to the Three Kings Islands.