In chemistry, a giant covalent structure is a chemical compound in which the atoms are held together by covalent bonds, but these bonds extend throughout the entire crystal lattice, rather than being localised between pairs of atoms. This results in a very strong and rigid structure.

The most common example of a giant covalent structure is diamond, in which each carbon atom is covalently bonded to its four nearest neighbours, forming a tetrahedral structure. This arrangement of atoms results in a very strong and hard material, which is used in a variety of industrial and technological applications, such as cutting tools and abrasives.

Other examples of giant covalent structures include graphite, silicon carbide, and quartz.