Designed and painted in 'the antique manner' by James 'Athenian' Stuart, the Painted Room at Spencer House is one of the most famous eighteenth century interiors in England. It is also the earliest complete neo-classical ensemble in Europe as, begun c. 1759, it was largely completed by November 1765. A wide range of sources was drawn upon for the design: Herculaneum, Antique Rome, Raphael's Vatican Loggie, and classical landscape painting.

The decorative theme of the room is a celebration of the Triumph of Love, in particular of Lord and Lady Spencer's own happy marriage, and the subjects of music, drinking and dancing nymphs are depicted in the festive and carefree decorations on the walls and ceiling.

The theme of marriage runs throughout the room, the chimneypiece frieze is painted with a copy of the Aldobrandini Wedding, a Roman painting excavated in 1605, and in the apse Stuart designed a circular grisaille panel of a Greek wedding based on a marble relief he discovered on the Acropolis.