Henry (Harry) John Cockayne Cust (1861 – 1917) was an English journalist and poet, and a Member of Parliament for the Unionist Party (i.e. Conservative Party), for Stamford, Lincolnshire 1890-1895, and for Bermondsey, 1900-1906.
He was educated at Eton College and Trinity College, Cambridge, and then was called to the Bar. He edited the Pall Mall Gazette from 1892 to 1896.
Cust was one of The Souls, and attached to Pamela Wyndham (who later married Edward Tennant ). Others in the clique were Margot Asquith, Arthur Balfour, George Curzon, Alfred Lyttelton, Godfrey Webb , and George Wyndham. He was the reputed natural father of Lady Diana Manners.
He married in 1893 Emmeline Mary Elizabeth Welby-Gregory (1867 - 1955), known as Nina, who was the daughter of Victoria, Lady Welby. She was a translator and editor of her mother's papers. They are buried together in Belton, Lincolnshire, with a monument designed by Nina.
During World War I he was active in propaganda on behalf of the British Government.