Cinnamon is a spice obtained from the inner bark of several tree species from the genus Cinnamomum. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, in particular sweet and savoury dishes such as biscuits, breakfast cereals, snack foods, bagels, teas, hot chocolate, and traditional foods. The aroma and flavour of cinnamon derive from its essential oil and principal component, cinnamaldehyde, as well as numerous other constituents, including eugenol.

Cinnamon is the name for several species of trees and the commercial spice products that some of them produce. All are members of the genus Cinnamomum in the family Lauraceae. Only a few Cinnamomum species are grown commercially for spice. Cinnamomum verum (alternatively C. zeylanicum), known as "Ceylon cinnamon" after its origins in Sri Lanka (formerly Ceylon), is considered to be "true cinnamon", but most cinnamon in international commerce is derived from four other species, usually and more correctly referred to as "cassia": C. burmanni (Indonesian cinnamon or Padang cassia), C. cassia (Chinese cinnamon or Chinese cassia), C. loureiroi (Saigon cinnamon or Vietnamese cassia), and the less common C. citriodorum (Malabar cinnamon).

In 2023, world production of cinnamon was 238,403 tonnes, led by China with 39% of the total.