A pyx is a small container used by Catholic churches to carry the consecrated Eucharist to the sick or invalid. While the word is often applied to any covered carrier,the modern usage refers to small, flat, and metallic clamshell-style containers.The latter usually is used together with a monstrance. For this purpose, the front and back covers are made usually with glass. A fabric, purselike carrier is known as a purse, while the permanent containers within the church are tabernacles.

The word pyx comes from the Greek word pyxis meaning wooden receptacle. The latter is usually used together with a monstrance.