The Ghent Altarpiece (or the Adoration of the Mystic Lamb, Dutch: Het Lam Gods) is a very large and complex 15th-century Early Flemish polyptych altarpiece in St Bavo's Cathedral, attributed to the brothers Hubert and Jan van Eyck, and considered a masterpiece of European art and one of the world's treasures.
The panels are organised in two vertical registers, each with two sets of foldable wings with inner and outer panel paintings. The upper register of the inner panels contains form the central Deësis of Christ the King, Virgin Mary and John the Baptist. They are immediarly flanked, in the next panels by music playing angels, and, on the far outermost panels, the naked figures of Adam and Eve. The four lower-register panels are divided into two pairs; sculptural grisaille paintings of St John the Baptist and St John the Evangelist, and on the two outer panels, donor portraits of Joost Vijdt and his wife Lysbette Borluut. The central panel of the lower register shows a gathering of saints, sinners, clergy and soldiers attendant at an adoration of the Lamb of God. There are several groupings of figures, overseen by the dove of the Holy Spirit.
Art historians generally agree that the overall structure was designed by Hubert in the early to mid 1420s, and that the panels were painted by his younger brother Jan between 1430 and 1432. One of the most renowned and important paintings in art history, generations of art historians have attempted to attribute specific passage to either brother, however no convincing separation has been established. The altarpiece was commissioned by the merchant and Ghent mayor Jodocus Vijd and his wife Lysbette as part of a larger project for the Saint Bavo Cathedral chapel. The altarpiece's installation was officially celebrated on 6 May 1432. It was much later moved for security reasons to the principal cathedral chapel, where it remains. While indebted to the International Gothic as well as Byzantine and Romanic traditions, the altarpiece represented a huge advancement in art, in which the idealisation of the medieval tradition gave way to an exacting observation of nature and human representation. A now lost inscription on the frame stated that Hubert van Eyck maior quo nemo repertus (greater than anyone) started the altarpiece, but that Jan van Eyck—calling himself arte secundus (second best in the art)—completed it in 1432. The original, very ornate carved outer frame and surround, presumably harmonizing with the painted tracery, was destroyed during the Reformation; it may have included clockwork mechanisms for moving the shutters and even playing music.