John Harry Gerald Ruston OGS (1 October 1929 – 27 April 2010) was the 13th Bishop of St Helena from 1991 to 1999. He was previously Bishop Suffragan of Pretoria.
Ruston was born 1 October 1929 and grew up at Berkhamsted, Hertfordshire, where he was associated with the Parish of St Michael and All Angels, Sunnyside, before, during and just after World War II.
Ruston studied at Sidney Sussex College, Cambridge University, where he graduated with a Bachelor of Arts degree in 1952 and a Master of Arts degree in 1956. He also attended Ely Theological College in 1952.
Ruston was ordained a deacon in 1954 and a priest in 1955 in the Diocese of Leicester where he served a curacy at St Andrew’s Leicester from 1954 to 1957. He furthered his theological studies at Cuddesdon, where he was also a tutor, from 1957 to 1961.
Going to South Africa, Ruston was curate of Sekhukhuneland from 1967 to 1970, serving simultaneously as principal of St Francis’ College in Sekhukhuneland. Also from 1967 he served as an examining chaplain to the Bishop of Pretoria, a role he fulfilled until 1976. In 1971 he became the sub-dean at St Alban's Cathedral, Pretoria, of which he was a canon from 1968 to 1976.
In 1976 Ruston took up an appointment as Archdeacon of Bloemfontein and as an examining chaplain to the Bishop of Bloemfontein and warden and chaplain of St Michael’s School, Bloemfontein.