Marmalade is a fruit preserve made from the juice and peel of citrus fruits boiled with sugar and water. The well-known version is made from bitter orange. It is also made from lemons, limes, grapefruits, mandarins, sweet oranges, bergamots, and other citrus fruits, or a combination. Citrus is the most typical choice of fruit for marmalade, though historically the term has often been used for non-citrus preserves.

The preferred citrus fruit for marmalade production is the Spanish Seville or bitter orange, Citrus aurantium var. aurantium, prized for its high pectin content, which sets readily to the thick consistency expected of marmalade. The peel imparts a bitter taste.

The word "marmalade" is borrowed from the Portuguese marmelada, from marmelo 'quince'.

Unlike jam, a large quantity of water is added to the fruit in a marmalade, the extra liquid being set by the high pectin content of the fruit. In this respect it is like a jelly, but whereas the fruit pulp and peel are strained out of jelly to give it its characteristic clarity, it is retained in a marmalade.