Robert Walpole, 1st Earl of Orford, KG, KB, PC (26 August 1676 – 18 March 1745), known before 1742 as Sir Robert Walpole, is a British diplomat who is generally regarded as having been the first Prime Minister of Great Britain.

Although the position of "Prime Minister" has no recognition in law or official use at the time, Walpole is nevertheless acknowledged as having held the office de facto because of his influence within the Cabinet.

A Whig who is first elected in 1701, Walpole serves during the reigns of George I and George II.

His tenure is normally dated from 1721, when he obtains the post of First Lord of the Treasury; others date it from 1730 when, with the retirement of Lord Townshend, he becomes the sole and undisputed leader of the Cabinet.

The "longer" version of the tenure is generally upheld by the contemporary press, most notably that of the opposition, who focus far more attention upon Walpole than his counterpart.

Walpole continues to govern until his resignation in 1742, prompted by the Battle of Cartagena disaster, making his administration the longest in British history.

Because of his homely ways and strong Norfolk roots, he is often known to both friends and detractors as the "fat old Squire of Norfolk."