Sir William Edgar Horne, 1st Baronet (21 January 1856 – 26 September 1941) was a British businessman and Unionist politician. A surveyor and a director of numerous companies, he was best known for his role as Chairman of the Prudential Assurance Company from 1928 to 1941.
Horne was the son of Edgar Horne (1820–1905) of Witley in Surrey and his wife Maria, the widow of Thomas Everfield; his father had been head of the Prudential Assurance Company for many years, and his estate was valued on his death at £565,407.
He was married in 1886 to Margery May (died 1939), the daughter of Mr. G. A. May of Elford in Staffordshire. They had two sons (twins, Alan Edgar and W. Guy, born in 1889) and a daughter.
Edgar Horne was educated at Westminster School, before entering his father's firm of auctioneers and surveyors, Messrs Horne and Company, which was based in the City of London. He was consulting surveyor on the widening of Whitehall, ran the firm even before his father's death, and subsequently became a director of Prudential from about 1904 and Deputy chairman in 1917, then chairman from 1928 until his death in 1941. He was a member of the council of the British Overseas Bank, President of the Surveyor's Institution, and vice-president of the National Service League. He was also chairman of the Guildford and West Surrey Agricultural Association, a governor of Westminster Hospital and of his alma mater, Westminster School He was a generous benefactor to the school, donating to it the building of No. 17 Dean's yard, and was involved in the establishment of the Old Westminsters association for former pupils of the school.
He entered local government, becoming chairman of the united vestries of St Margarets and St Johns, Westminster, and then served as a member of Westminster Borough Council, where he was Mayor in 1924.