Pantaleon, who reigns in Arachosia, some time between 190 BCE and 180 BCE, is one of the most enigmatic of the Greek kings in Bactria and India.

A younger contemporary or successor of the Greco-Bactrian king Demetrius, he is sometimes believed to have been his brother and/or subking.

He is the first Greek king to strike Indian coins, peculiar irregular bronzes which suggests he has his base in Arachosia and Gandhara and wants support from the native population.

The limited size of his coinage indicates a short reign.

Known evidence suggests that he is replaced by his (probable) brother or son Agathocles, by whom he is commemorated on a "pedigree" coin.

Some of his coins (as well as those of Agathocles and Euthydemus II) have another surprising characteristic: these kings are the first in the world to issue coins of copper-nickel (75/25 ratio) alloy, a technology that will not be developed in the West until the eighteenth century, but is known by the Chinese at this time, as some weapons from China’s Warring States Period are known to have been made from the copper-nickel alloy known as "white copper".

This suggests that exchanges of the metallic alloy, or possibly exchanges of technicians, are occurring at this time between China and the region of Bactria.

The practice of exporting Chinese metals, in particular iron, for trade is attested around this period.