Thaumatrope of flowers and vase, 1825.

A thaumatrope is a toy that was popular in Victorian times. A disk or card with a picture on each side is attached to two pieces of string. When the strings are twirled quickly between the fingers the two pictures appear to combine into a single image due to the phi phenomenon and persistence of vision.

Examples of common thaumatrope pictures include a bare tree on one side of the disk, and its leaves on the other, or a bird on one side and a cage on the other. They often also included riddles or short poems, with one line on each side. Thaumatropes were one of a number of simple, mechanical optical toys that used persistence of vision. They are recognized as important antecedents of cinematography and in particular of animation.

The coined name translates roughly as "wonder turner", from Ancient Greek: θαῦμα "wonder" and τρόπος "turn".

The invention of the thaumatrope is usually credited to either John Ayrton Paris or Peter Mark Roget. Paris used one to demonstrate persistence of vision to the Royal College of Physicians in London in 1824. He based his invention on ideas of the astronomer John Herschel and the geologist William Henry Fitton, and some sources attribute the actual invention to Fitton rather than Paris. Charles Babbage reported being introduced to the concept by Herschel and Fitton.

In 2012, it was reported that a prehistoric thaumatrope had been discovered in caves in France, particularly the Chauvet Caves.