Sir William Bruce of Kinross, 1st Baronet (c. 1630 – 1710), was a Scottish gentleman-architect, "the effective founder of classical architecture in Scotland," as Howard Colvin observes. As a key figure in introducing the Palladian style into Scotland, he has been compared to the pioneering English architects Inigo Jones and Christopher Wren, and to the contemporaneous introducers of French style in English domestic architecture, Hugh May and Sir Roger Pratt.

Bruce was a merchant in Rotterdam during the 1650s, and played a role in the Restoration of Charles II in 1659. He carried messages between the exiled king and General Monck, and his loyalty to the king was rewarded with lucrative official appointments, including that of Surveyor General of the King's Works in Scotland, effectively making Bruce the "king's architect". His patrons included John Maitland, 1st Duke of Lauderdale, the most powerful man in Scotland at that time, and Bruce rose to become a member of Parliament, and briefly sat on the Privy Council of Scotland.

Despite his lack of technical expertise, Bruce became the most prominent architect of his time in Scotland. He worked with competent masons and professional builders, to whom he imparted a classical vocabulary; thus his influence was carried far beyond his own aristocratic circle. Beginning in the 1660s, Bruce built and remodelled a number of country houses, including Thirlestane Castle for the Duke of Lauderdale, and Prestonfield House. Among his most significant work was his own Palladian mansion at Kinross, built on the Loch Leven estate which he had purchased in 1675. As the king's architect he undertook the rebuilding of the Royal Palace of Holyroodhouse in the 1670s, which gave the palace its present appearance. After the death of Charles II, Bruce lost political favour and later, following the accession of William and Mary, he was imprisoned more than once as a suspected Jacobite. However, he managed to continue his architectural work, often providing his services to others with Jacobite sympathies.

Little is known of William Bruce's youth, and his date of birth is unrecorded. He was probably born at Blairhall, now located in western Fife, in around 1630, the second son of Robert Bruce of Blairhall and Katherine Preston. He may have attended St Andrews University in 1637–1638, which would suggest that his birth date was as early as 1625. The Bruces were a well-connected Episcopalian family, strongly loyal to the king, and descended from Thomas Bruce, a cousin of King Robert II, who had been granted lands in Clackmannan and Fife. Bruce's first cousin Edward Bruce was created Earl of Kincardine in 1647.

Letters in the Earl of Kincardine's papers show that William Bruce was in exile in Rotterdam during the 1650s with his cousin, Alexander Bruce, brother of the Earl of Kincardine. As Episcopalians, William and Alexander would have sought refuge from the Puritan Commonwealth established by Oliver Cromwell. In Rotterdam, they were in contact with Sir Robert Moray, a soldier and natural philosopher close to Charles II, who then resided at Maastricht. William Bruce was a merchant, based in the Scottish community in Rotterdam, but traveling widely. He owned a ship with Alexander Bruce and John Hamilton of Grange, and was involved in the trade of wine, coal, and timber between Norway, France, England, Scotland and the Low Countries. He is recorded as having a house and a mistress in La Rochelle. He may have had a son Normand by this mistress since in 1672 he figures as a witness to the baptism at Holyrood of a William Bruce, son of Normand Bruce, mason. Moreover, the marriage record of Normand Bruce states that he was employed at Balcaskie. In 1658, William and Alexander traveled together from Bremen overland to Maastricht to meet Moray. Alexander Bruce and Moray were founder members of the Royal Society in 1660, and it is likely that architecture featured in their discussions, particularly the new town hall in Maastricht that Moray had recently advised on.

In 1659, Bruce acted as a messenger between General Monck, Cromwell's commander-in-chief in Scotland, and the exiled King Charles II. A passport survives, issued to Bruce by Monck in September 1659, and giving him permission to remain in Scotland until his "returne to Holland," and it appears that the messages he brought from Charles persuaded Monck to march his army to London, a decisive event in the Restoration. The nature of their communications is not known, although it would appear that Moray selected him for the task. Sir Robert Douglas stated that Bruce "painted the distress and distractions" of Scotland before the General, and suggested to him "the glory that would be acquired in restoring the royal family."

Following the restoration, William Bruce was appointed Clerk to the Bills in 1660, and Clerk of Supply to the Lords in Council in 1665. Both were lucrative positions, involving collection of fees, from Parliament in the first case, and from petitioners to the Court of Session in the latter. Meanwhile, Sir Robert Moray had established himself as a courtier and scientist at Whitehall, London, and employed Bruce as a trusted messenger between Whitehall and the Duke of Lauderdale, Secretary for Scotland.

Moray later served on the Treasury Commission for Scotland, as did Alexander Bruce, now Earl of Kincardine. Bruce reported to this commission as a revenue collector, and benefited from the patronage of its members. The Commission had responsibility for the King's Works, and in 1667 Bruce was appointed Superintendent and Overseer of the Royal Palaces in Scotland. Four years later he was made Surveyor General of the King's Works in Scotland, with a salary of £3600 Scots (£300 Sterling, or £ 61,000 in 2023), for the purpose of rebuilding Holyroodhouse. In March 1671, Bruce was part of a syndicate which bought the rights to collect taxes over a five-year period, paying £26,000 Sterling (£ 5.3 million in 2023) for the privilege. As such, it would appear that Bruce was not only the architect of Holyroodhouse, but one of the principal financiers of the £21,000 project.