A cookie is a small, flat, sweet, baked good, usually containing flour, eggs, sugar, and either butter, cooking oil or another oil or fat. It may include other ingredients such as raisins, oats, chocolate chips or nuts.

In most English-speaking countries except for the US and Canada, crisp cookies are called biscuits. Chewier cookies are commonly called cookies even in the UK. Some cookies may also be named by their shape, such as date squares or bars.