A circular cut diamond (10) comprising a girdle (20), a crown (30), and a pavilion (40). The crown (30) comprises a circumferential succession of eight main crown facets which extend upward from an upper edge (23) of the girdle at a crown angle which is greater than 19° and less than 25°. The pavilion (40) comprises a circumferential succession of eight main pavilion facets which extend downward from a lower edge (24) of the girdle at a pavilion angle which is greater than 41° and less than 43°. The circular cut diamond (10) can compete with the brilliance of an ideal cut diamond without a significant compromise in carat weight.