The Alchemist Discovering Phosphorus is a painting by Joseph Wright of Derby originally completed in 1771 then reworked in 1795.

[1] The full title of the painting is The Alchymist, in Search of the Philosopher's Stone, Discovers Phosphorus, and prays for the successful Conclusion of his operation, as was the custom of the Ancient Chymical Astrologers.

The picture shows the alchemist trying to produce the elusive Philosopher's stone, which could turn ordinary metal into gold, but instead, to his amazement, he discovers phosphorus.

However, Wright does not picture the alchemist in a 17th-century background, but he romanticises the room by imagining medieval gothic arches and high, pointed windows as if he is in a church.

The picture travelled with Wright to Italy in 1773–1775, came back to England, was reworked in 1795, but was only sold four years after his death, when his possessions were auctioned at Christie's.