The ZGMF-X666S Legend Gundam is a mobile suit introduced in the anime Mobile Suit Gundam SEED Destiny. It is piloted by Rey Za Burrel.

The direct successor of the ZGMF-X13A Providence Gundam, the Legend Gundam, unlike its predecessor, was designed with the use of the DRAGOON System in mind. As such, the layout and structure of its DRAGOON System was greatly improved. In addition, improvements in the operating system allowed pilots without high spatial awareness to use the DRAGOONs as well. Thanks to the two pairs of blade antennas on its head, the Legend Gundam also had enhanced intelligence gathering capabilities compared to its predecessor.

Developed as part of the Third Stage Series, the Legend Gundam's output far surpassed the Second Stage Series units due to its use of the Hyper-Deuterion Engine, a hybrid of nuclear power and the Deuterion Beam Energy Transfer System. However, since the Junius Treaty banned the use of nuclear engines, it was classified as part of the Second Stage Series due to political concerns (hence the "S" at the end of its model number).

In addition to the DRAGOONs, the Legend was armed with the MA-BAR78F high energy beam rifle, an improved version of the Providence's MA-M221 "Judicium" beam rifle, as well as a pair of MA-M80S Defiant Kai beam javelin, which could be connected to form a double-bladed beam saber known as the "ambidextrous halberd". It also had a pair of head-mounted CIWS, and like the ZGMF-X42S Destiny Gundam, was equipped with a pair of MX2351 "Solidus Fulgor" beam shield generators behind its hands for defense.