Henry VI planned a university counterpart to Eton College (whose chapel is very similar, but not on the scale intended by Henry). The King decided the dimensions of the Chapel. The architect of the chapel is disputed: Reginald Ely, who was commissioned in 1444 as the head press mason, was a possible architect; however, Nicholas Close (or Cloos) was recorded as the "surveyor", which has been generally accepted to be synonymous with architect. The first stone of the Chapel was laid, by Henry himself, on the Feast of St James the Apostle, 25 July 1446, the College having been begun in 1441. By the end of the reign of Richard III (1485), despite the Wars of the Roses, five bays had been completed and a timber roof erected. Henry VII visited in 1506, paying for the work to resume and even leaving money so that the work could continue after his death. In 1515, under Henry VIII, the building was complete but the great windows had yet to be made.
The chapel features the world's largest fan vault, constructed between 1512 and 1515 by master mason John Wastell. It also features fine medieval stained glass and, above the altar, The Adoration of the Magi by Rubens, originally painted in 1634 for the Convent of the White Nuns at Louvain in Belgium. The painting was installed in the Chapel in 1968; this involved the destruction and lowering of the Sanctuary floor leading up to the High Altar. It was previously believed that gradations were created in 1774 by James Essex, when Essex had in fact lowered the floor by 5 1/2 inches, but at the demolition of these steps, it was found that the floor instead rested on Tudor brick arches. The installation of the painting also resulted in the destruction and loss of the Edwardian reredos, which was then well-liked by the public. During the demolition of these Tudor steps, built at the Founder's specific request that the high altar should be 3 ft above the choir floor, human remains in intact lead coffins with brass plaques were discovered, dating from the 15th to 18th centuries, and were disinterred. The eventual installation of the Rubens was also not without problems: once seen beneath the east window, a conflict was felt between the picture's swirling colours and those of the stained glass. The Rubens was also a similar shape to the window, which "dwarfed it and made it look rather like a dependent postage stamp". Plain shutters were proposed, one on each side, to give it a triptych shape (although the picture was never part of a triptych) and lend it independence of form, which is how one sees the Rubens today.
During the Civil War the chapel was used as a training ground by Oliver Cromwell's troops, but escaped major damage, possibly because Cromwell himself, being a Cambridge student, gave orders for it to be spared. Graffiti left by these soldiers is still visible on the north and south walls near the altar. During World War II most of the stained glass was removed and the chapel again escaped damage.
The windows of King's College Chapel are some of the finest in the world from their era. There are 12 large windows on each side of the chapel, and larger windows at the east and west ends. With the exception of the west window, they are by Flemish hands and date from 1515 to 1531. Barnard Flower, the first non-Englishman appointed as the King's Glazier, completed four windows. Gaylon Hone and three partners (two English and one Flemish) are responsible for the east window and 16 others between 1526 and 1531. The final four were made by Francis Williamson and Symon Symondes. The one modern window is that in the west wall, which was donated by King's alumnus Francis Stacey and is by the Clayton and Bell company and dates from 1879.
This large wooden screen, which separates the nave from the altar and supports the chapel organ, was erected in 1532–36 by Henry VIII in celebration of his marriage to Anne Boleyn. The screen is an example of early Renaissance architecture: a striking contrast to the Perpendicular Gothic chapel; Sir Nikolaus Pevsner said it is "the most exquisite piece of Italian decoration surviving in England".