Pantaleon, also known as Panteleimon, (Greek: Πανταλέων) was a Greek king who reigned some time between 190–180 BC in Bactria and India. He was a younger contemporary or successor of the Greco-Bactrian king Demetrius, and is sometimes believed to have been his brother and/or subking.
The scarcity of his coinage indicates a short reign. Known evidence suggests that he was replaced by his (probable) brother or son Agathocles, by whom he was commemorated on a "pedigree" coin.
Some of his coins (as well as those of Agathocles and Euthydemus II) have another surprising characteristic: they are made of copper-nickel alloy, a technology that would not be developed in the West until the 18th century, but was known by the Chinese at the time. This suggests that exchanges of the metallic alloy or technicians happened between China and the region of Bactria.
He was the first Greek king to strike Indian coins, peculiar irregular bronzes representing a lion with a dancing Indian woman, probably the goddess Lakshmi (a type also known in the Post-Mauryan coinage of Gandhara), which suggests he had his base in Arachosia and Gandhara and wanted support from the native population.