Walter Steward of Dundonald (died 1246) was 3rd hereditary High Steward of Scotland and Justiciar of Scotia.
He was the eldest son of Alan fitz Walter, 2nd High Steward of Scotland by his second wife Alesta of Mar. He was the first member of the House of Stuart to use Stewart as a surname and was designated "of Dundonald".
The House of Stuart, originally spelt Stewart, also known as the Stuart dynasty, was a royal house of Scotland, England, Ireland and later Great Britain. The family name comes from the office of High Steward of Scotland, which had been held by the family progenitor Walter fitz Alan (c. 1150). The name Stewart and variations had become established as a family name by the time of his grandson Walter Stewart. The first monarch of the Stewart line was Robert II; he and his descendants were monarchs of Scotland from 1371 and of England, Ireland and Great Britain from 1603, until 1714. Mary, Queen of Scots (r. 1542–1567), was brought up in France where she adopted the French spelling of the name Stuart.
In 1503, James IV married Margaret Tudor, thus linking the reigning royal houses of Scotland and England. Margaret's niece, Elizabeth I of England died without issue in 1603, and James IV's and Margaret's great-grandson James VI of Scotland acceded to the thrones of England and Ireland as James I in the Union of the Crowns. The Stuarts were monarchs of Britain and Ireland and its growing empire until the death of Queen Anne in 1714, except for the period of the Commonwealth between 1649 and 1660.