Sir Rupert Charles Hart-Davis (28 August 1907 – 8 December 1999) was an English publisher and editor. He founded the publishing company Rupert Hart-Davis Ltd. As a biographer, he is remembered for his Hugh Walpole (1952), as an editor, for his Collected Letters of Oscar Wilde (1962), and, as both editor and part-author, for the Lyttelton/Hart-Davis Letters.

Working at a publishing firm before the Second World War, Hart-Davis began to forge literary relationships that would be important later in his career. Founding his publishing company in 1946, Hart-Davis was praised for the quality of the firm's publications and production; but he refused to cater to public tastes, and the firm eventually lost money. After relinquishing control of the firm, Hart-Davis concentrated on writing and editing, producing collections of letters and other works which brought him the sobriquet "the king of editors".

Hart-Davis was born in Kensington, London. He was legally the son of Richard Hart-Davis, a stockbroker, and his wife Sybil née Cooper, but by the time of his conception the couple were estranged, though still living together, and Sybil Hart-Davis had many lovers at that time. Hart-Davis believed the most likely candidate for his natural father to be a Yorkshire banker called Gervase Beckett. As a child, Rupert Hart-Davis and his sister Deirdre Hart-Davis were drawn by Augustus John and painted by William Nicholson (1912).

Hart-Davis was educated at Eton and Balliol College, Oxford, though he found university life not to his taste and left after less than a year.

Hart-Davis decided to become an actor, and he studied at The Old Vic, where he came to realise that he was not a talented enough actor to succeed, and he turned instead to publishing in 1929, joining William Heinemann Ltd. as an office boy and assistant to the managing director Charley Evans. He spent two years with Heinemann and a year as manager of the Book Society; during this period, he built up good relationships with a number of authors and was able to negotiate a directorship for himself at Jonathan Cape Ltd.

In his seven years with Cape, Hart-Davis recruited a successful group of authors ranging from the poets William Plomer, Cecil Day-Lewis, Edmund Blunden and Robert Frost, to the humorist Beachcomber. He was well placed to secure Duff Cooper's life of Talleyrand, as Cooper was his uncle. As the junior partner at Cape, he had to handle their difficult authors including Robert Graves, Wyndham Lewis and Arthur Ransome, the last being seen as difficult because of his wife Genia, with her "distrustfulness, venom and guile". Hart-Davis was a close friend of Ransome, sharing an enthusiasm for cricket and rugby. After Cape's death in 1960 Hart-Davis commented to George Lyttelton that Cape had been "one of the tightest-fisted old bastards I've ever encountered". The second partner, Wren Howard, was "even tighter" than Cape, and neither of them liked fraternising with authors, which they left to Hart-Davis.

In World War II Hart-Davis volunteered for military service as a private soldier, but was soon commissioned into the Coldstream Guards. He did not see active service, never being stationed more than 25 miles from London.

After the war, Hart-Davis was unable to obtain satisfactory terms from Jonathan Cape to return to the company, and in 1946 he struck out on his own, founding Rupert Hart-Davis Ltd, in partnership with David Garnett and Teddy Young and with financial backing from Eric Linklater, Arthur Ransome, H. E. Bates, Geoffrey Keynes, and Celia and Peter Fleming. His own literary tastes dictated which books were accepted and which rejected. Frequently he turned down commercial successes because he thought little of the works' literary merit. He later said, "I usually found that the sales of the books I published were in inverse ratio to my opinion of them. That's why I established some sort of reputation without making any money."