Sir Horace (Horatio) Mann, 1st Baronet KB (c. 25 August 1706 – 6 November 1786), diplomat, was a long-standing British resident in Florence.
He was the second son of Robert Mann (1678–1751), a successful London merchant, and his wife. He was brought up at Chelsea, and educated at Eton College and later, briefly, at Clare College, Cambridge.
Suffering from poor health, he travelled on the continent in the 1730s. In February 1737, he was appointed as secretary to Charles Fane, the British Minister at Florence. He then served as British diplomatic representative there to the Grand Dukes of Tuscany for the rest of his life. In the course of his long diplomatic career, he was Chargé d'affaires in 1738-1740; Minister between 1740 and 1765; Envoy Extraordinary from 1767; and finally Envoy Extraordinary and Plenipotentiary from 1782 until his death.
As Great Britain had no diplomatic representation at Rome, Mann's duties included reporting on the activities of the exiled Stuarts, the Old Pretender and the Young Pretender.
He kept an open house for British visitors at Florence, inviting them for conversazione when there was no performance at the theatre. His generosity and kindness was universally acknowledged, although his close friendship with the painter Thomas Patch (expelled from Rome after a homosexual incident) reflected on his reputation. He met Horace Walpole (to whom he was distantly related) in 1739, and conducted a now-renowned correspondence with him over forty years, though they last met in 1741. The correspondence was published by Lord Dover in 1833.