Cardiidae is a family of marine bivalve mollusks commonly known as cockles or heart clams. The name Cardiidae comes from the Greek word "kardia" which means heart, referring to the shell shape of many species in this family that resembles a heart.

Members of this family have two equal-sized shells, or valves, that are typically rounded and convex in shape. They have a distinctive set of muscle scars on the inside of the shell called "pallial lines" which are used to identify different species. Cardiids are filter feeders, using their gills to extract food particles from the water.

Cardiidae species can be found in a variety of habitats, including sandy and muddy seafloors, and some live in shallow waters while others can be found at depths of several thousand meters. Some well-known cardiid genera include Cardium, Cerastoderma, and Laevicardium.