Sodium_chloride_crystal.png|thumb|right|Sodium chloride (halite) crystal structure. Each atom has six nearest neighbors, with octahedral geometry. This arrangement is known as cubic close packed (ccp).
Light blue = Na⁺
Dark green = Cl^-]]

An ionic crystal is a crystal consisting of ions bound together by their electrostatic attraction. Examples of such crystals are the alkali halides, including potassium fluoride, potassium chloride, potassium bromide, potassium iodide, sodium fluoride, and other combinations of sodium, caesium, rubidium, or lithium ions with fluoride, bromide, chloride or iodide ions.

They are characterized by strong absorption of infrared radiation and have planes along which they cleave easily.

Cristal ionique | イオン結晶