A nutcracker is a tool designed to open nuts by cracking their shells. There are many designs, including levers, screws, and ratchets. The lever version is also used for cracking lobster and crab shells.

A nut is a fruit consisting of a hard or tough nutshell protecting a kernel which is usually edible. In general usage and in a culinary sense, a wide variety of dry seeds are called nuts, but in a botanical context "nut" implies that the shell does not open to release the seed (indehiscent).