Saint Margaret of Scotland (c. 1045 – 16 November 1093) was an English princess of the House of Wessex, the sister of Edgar Ætheling.

According to the Life of Saint Margaret, attributed to Turgot of Durham, she died at Edinburgh Castle in 1093, just days after receiving the news of her husband's death in battle.

[3] It was originally thought that St Margaret herself worshipped in this small chapel, but the style of the architecture indicates that it was built during the reign of David I, her fourth son, who ruled from 1124–1153.

[4] The chapel formed part of a larger building, located to the north, which contained the castle's royal lodgings.

On his death bed in 1329, Bruce spoke of the story of Queen Margaret and issued orders for the chapel's repair, with some forty pounds Scots being put aside for that purpose.

The rectangular structure with an internal width of 3 metres (10 ft) has an entrance door at one side near the back of the nave which is 4.87 m (16 ft) long, then a typically Romanesque round chancel arch 1.52 m (5 feet) wide with chevron mouldings decorating the arch above columns on each side leads into an apsed sanctuary 3 m long, with the apse having a radius of 1.52 m. The north wall has been renewed, and the three surviving outer walls are 61 cm (2 ft) thick, as is the chancel wall.