The Lord Steward or Lord Steward of the Household is one of the three Great Officers of the Household of the British monarch. He is, by tradition, the first great officer of the Court and he takes precedence over all other officers of the household.

Historically the Lord Steward oversaw over the Household 'below stairs'. He also presided at the Board of Green Cloth, which in early centuries had a financial, administrative and judicial role (latterly the Board retained a vestigial legal remit, until it was finally abolished in a 2004 reform of local government licensing). Prior to 1924 the Lord Steward was always a member of the Government, and until 1782 the office had been one of considerable political importance and carried Cabinet rank. In the modern period, Lord Stewards (up to and including Hugh Percy, 10th Duke of Northumberland in 1973) were invariably made Privy Counsellors on appointment.

Over time the domestic responsibilities of the office came increasingly to be carried out by a subordinate officer: the Master of the Household. In the Royal Household reforms of the 1920s, the Lord Steward's Department was renamed the Master of the Household's Department. At the same time, Lord Steward ceased to be a political appointment and instead became a largely titular office in the gift of the monarch.

The Lord Steward continues to be in regular attendance on State and other ceremonial occasions (including State visits, State banquets, the State Opening of Parliament, State Funerals and Coronations). Holders of the office are always peers, usually of or above the degree of an Earl. Each Lord Steward receives his appointment from the Sovereign in person and bears a white staff as the emblem and warrant of his authority. The incumbent Lord Steward (appointed in 2023) is Peter St Clair-Erskine, 7th Earl of Rosslyn (who additionally serves as Personal Secretary to Their Majesties The King and Queen).

Within the Curia Regis, the office of Steward of the King's Household was indistinguishable from that of Lord (High) Steward of England, which had first been introduced to the realm under William the Conqueror (and which was by the end of the 12th century an hereditary office). As late as 1221 the hereditary stewardship was still being referred to as a 'stewardship of the royal household'.

Under King John, however, the holder of the hereditary office (Simon de Montfort, 5th Earl of Leicester) resided in France, and after his death in 1218 the Earldom went into 'virtual abeyance' until Simon de Montfort, 6th Earl of Leicester had his claim to it confirmed in 1239. By that time it had become the norm to appoint separate Stewards of the Household to undertake the practical duties of the office (so de Montfort came to be referred to, by contrast, as 'Steward of all England'). For the rest of the 13th century there were normally two Stewards of the Household appointed, until 1292 when Walter de Beauchamp continued in office alone after his co-steward Peter de Champvent had been made Chamberlain. Since then every Steward of the Household has served singly.

During the minority of King Richard II, the Crown assented to a proposal that the Chancellor and Treasurer of England, the Lord Keeper of the Privy Seal and the Steward and Chamberlain of the Household should be chosen by Parliament 'from the ablest persons in the Realm', and remain in office until the next Parliament (in contrast to the hereditary offices of State).

During the reign of King Edward IV, the duties, privileges and precedence of the Lord Steward were comprehensively enumerated in the Black Book of the Household (compiled in the early 1470s). In it he is described as having, under the King, the 'secondary estate and rule' of the Royal Household, which is 'wholly committed to be ruled and guided by his reason'.