Backing onto the right hand side of the main doorway is the Founder’s Chapel. It was not part of the original plan of the Monastery, and instead owes its construction to the decision of King João I to build a family pantheon, giving the master builder Huguet the job of its planning and construction, which was completed in about 1433/34. It is a space full of historical and artistic significance. On its completion, for the first time in Portugal there was a place exclusively destined for the function of royal pantheon. Its architectural and sculptural choices are important. From a basic quadrangular plan, it changes in the centre into an octagon covered with a complex star-shaped vaulted ceiling which functions as a truly splendid canopy for King João I and Queen Filipa de Lencastre, who lie within a grandiose arched tomb.
On the lid of what is the largest 15th century gothic sarcophagus in Portugal are sculpted the royal couple in repose, holding hands, covered by baldachins with their coat of arms; on the trim, between branches and leaves, their mottos “Y me plet” and “por bem”; on the front two long inscriptions in Latin that summarise their merits and achievements; on the headpiece the cross of the Order of Jarreteira (which King João received) with the inscription “hinny soit qui mal y pense”.
At the far wall on the south side, are the tombs, from the second quarter of the 15th century of the children of the royal couple, the ‘illustrious generation’ as Camões called them. From right to left: the tomb of the Infante and Regent Pedro and his wife Isabel de Urgel, duchess of Coimbra; Henry the Navigator and Master of the Order of Christ (with its own statue in repose); the Infante João, master of the Order of Santiago and his wife Isabel; Fernando, master of the Order of Avis, who died in captivity in Fez and became known as the Holy or Saintly Prince.
The three tombs found on the eastern side of the Chapel are from the beginning of the 20th century, commissioned by King Carlos I. Here are buried, from left to right: King Afonso V, grandson of João I; King João II, son of Afonso V; and finally the prince and heir to the throne Afonso, son of João II, who died suddenly in 1491 in a horse-riding accident in the region of Santarém.