John Codman Ropes was an American military historian and lawyer, and the co-founder of the law firm Ropes & Gray.

John Colin Dunlop FRSE (1785–1842) was a Scottish advocate and historian.

John Corbin was an American dramatic critic and author.

John Cordy Jeaffreson was an English novelist and author of popular non-fiction. He also spent periods teaching and as an inspector of historical documents.

John Cowper Powys was an English philosopher, lecturer, novelist, critic and poet born in Shirley, Derbyshire, where his father was vicar of the parish church in 1871–1879. Powys appeared with a volume of verse in 1896 and a first novel in 1915, but gained success only with his novel Wolf Solent in 1929. He has been seen as a successor to Thomas Hardy, and Wolf Solent, A Glastonbury Romance (1932), Weymouth Sands (1934), and Maiden Castle (1936) have been called his Wessex novels. As with Hardy, landscape is important to his works. So is elemental philosophy in his characters' lives. In 1934 he published an autobiography. His itinerant lectures were a success in England and in 1905–1930 in the United States, where he wrote many of his novels and had several first published. He moved to Dorset, England, in 1934 with a US partner, Phyllis Playter. In 1935 they moved to Corwen, Merionethshire, Wales, where he set two novels, and in 1955 to Blaenau Ffestiniog, where he died in 1963.

John Dann MacDonald was an American writer of novels and short stories. He is known for his thrillers.

John Davison Rockefeller Sr. was an American business magnate and philanthropist. He has been widely considered the wealthiest American of all time and the richest person in modern history. Rockefeller was born into a large family in Upstate New York who moved several times before eventually settling in Cleveland. He became an assistant bookkeeper at age 16 and went into several business partnerships beginning at age 20, concentrating his business on oil refining. Rockefeller founded the Standard Oil Company in 1870. He ran it until 1897 and remained its largest shareholder.

John Davidson was a Scottish poet, playwright and novelist, best known for his ballads. He also did translations from French and German. In 1909, financial difficulties, as well as physical and mental health problems, led to his suicide.

John Denham Parsons was an English writer and Shakespeare authorship theorist.

John Dewey was an American philosopher, psychologist, and educational reformer. He was one of the most prominent American scholars in the first half of the twentieth century.