Sir William Henry Mahoney Christie FRS (1 October 1845 – 22 January 1922) was a British astronomer.
He was born in Woolwich, London, the son of Samuel Hunter Christie and educated at King's College School, King's College London, and at Trinity College, Cambridge. He was fourth wrangler in 1868 and elected a fellow of Trinity in 1869.
Having been Chief Assistant at the Royal Observatory at Greenwich from 1870 to 1881, he was appointed to replace George Airy as Astronomer Royal in 1881 and remained in office until 1910. He was made a Knight Commander of the Order of the Bath in 1904. He was elected a Fellow of the Royal Society in June, 1881. He was president of the Royal Astronomical Society from 1888 to 1890.
The first Astronomer Royal to retire at 65 (all previous incumbents bar Airy and John Pond had died in office; John Pond had been forced by poor health to resign in 1835, while Airy retired aged 81), Christie died and was buried at sea near Gibraltar in 1922. He had married in 1881 Mary Violette, daughter of Sir Alfred Hickman.
At a meeting of the Astronomical and Physical Society of Toronto on 1891-12-01 a letter was received from Dr. Christie, reading, "It will give me much pleasure to accept the nomination as Honourary Member of the Astronomical and Physical Society of Toronto, with which you propose to honour me; and if elected, I shall highly esteem the distinction which your Society confers upon me." On motion of Mr. Arthur Harvey, seconded by Dr. G.B. Foster, Dr. Christie, Astronomer Royal of England, was elected an Honourary Member. In addition to his complimentary references to Dr. Christie, Mr. Harvey dwelt upon the signal honour done the Society by the very cordial manner in which invitations to become associated with it had been acceded to by such eminent astronomers as Dr. Christie, Dr. Newcomb, Dr. Huggins, Dr. Holden, Miss Clerke, and the other ladies and gentlemen nominated and elected.
Dr. Sir Wm. Henry Mahoney