A poison ring or pillbox ring is a type of ring with a container under the bezel or inside the bezel itself that could be used to hold poison or another substance. They became popular in Europe during the sixteenth century. The poison ring was used either to slip poison into an enemy's food or drink, or to facilitate the suicide of the wearer in order to escape capture or torture.

Rings like this have been used throughout history to carry perfume, locks of hair, devotional relics, messages and other keepsakes, so they have also been known by other names. Artists would paint tiny portraits of loved ones, to be carried in what was called a “locket ring,” which was popular during the Renaissance.
This type of jewelry originated in ancient days of the Far East and India. It replaced the practice of wearing keepsakes and other items in pouches around the neck. The wearing of vessel rings was so practical that it spread to other parts of Asia, the Middle East and the Mediterranean before reaching Western Europe in the Middle Ages. By then the rings were part of the “holy relic trade.”