A cut gemstone having 56 to 58 facets to maximize the volume of light that is reflected from the inside and thus produce the greatest brilliance. The most common shape of brilliant cut stones are round, which is why this is type of cut is sometimes called a "round-cut", but oval, marquise, pear shape and heart shapes are not unusual.

This gem cut, originally the Mazarin diamond cut developed in the mid-1700s, has undergone a long evolution. There are currently hundreds of variations of the round brilliant cut but the term usually refers to the modern American Ideal cut designed by Marcel Tolkowsky. It usually features 57 triangular “brilliant” facets and one flat table facet.

The most brilliant cut containing 58 facets. The round brilliant cut makes the most efficient use of light to increase brilliance and fire.