John Tudor ("Jack") Gwynn (13 November 1881 in Ramelton, County Donegal, Ireland – 17 May 1956 in Bangor, County Down, Northern Ireland) was the seventh son of the Very Rev John Gwynn D.D. and Lucy Josephine O’Brien. He was born at Ramelton, County Donegal, while his father was Dean of Raphoe. Following in the footsteps of his elder brothers he was educated at St Columba's College, Rathfarnham and Trinity College, Dublin. Like the three brothers immediately preceding him, Lucius, Arthur and Robin, he was an outstanding cricketer, and like them he in his turn captained first the St Columba’s XI and then the Dublin University XI. He did not however go on to represent the Ireland cricket team internationally.
After graduating Jack Gwynn joined the Indian Civil Service. He started his first tour of duty in India in 1905. During a period of home leave Jack became engaged to Joan Sedding, a relative through marriage of his elder brother Lucius. Joan’s father was the ecclesiastical architect John Sedding. Both of Joan’s parents had died while Joan was in her infancy and she had been brought up by a maternal aunt and uncle, the Rawlinsons; her cousin Katharine, the one who had married Lucius Gwynn, was like an elder sister to her and probably had a hand in arranging the match. Jack and Joan’s wedding took place in Colombo in 1912.
While working in the Indian Civil Service Jack Gwynn represented the "Europeans" in two first-class matches against the "Indians" in 1919 and 1920.
At the outbreak of the first World War Jack and Joan Gwynn were on home leave. Jack was retained in London and placed on special duty at the Admiralty. It was during this period in England that the couple’s three children were born: Peter (1916), Rose (1918) and Katharine (1920).