Christmas ornaments are decorations (usually made of glass, metal, wood or ceramics) that are used to festoon a Christmas tree. Ornaments take many different forms, from a simple round ball to highly artistic designs. Ornaments are almost always reused year after year, rather than purchased annually, and family collections often contain a combination of commercially produced ornaments and decorations created by family members. Such collections are often passed on and augmented from generation to generation.

Santa Claus is a commonly used figure. Candy canes, fruit, animals, snowmen, angels and snowflake imagery are also popular choices.

Lucretia P. Hale's story "The Peterkins' Christmas-Tree" offers a short catalog of the sorts of ornaments used in the 1870s:

The modern-day mold-blown colored glass Christmas ornament was originally invented in the small German town of Lauscha in the mid-19th century.

A bauble is a spherical decoration that is commonly used to adorn Christmas trees. The bauble is one of the most popular Christmas ornament designs, and they have been in production since 1847. Baubles can have various designs on them, from "baby's first Christmas," to a favorite sports team. Many are plain, being simply a shiny sphere of a single color.