George Robertson Sinclair (28 October 1863 – 7 February 1917) was an English cathedral organist, who served at Truro and Hereford cathedrals.
As a young man, Sinclair was destined for the Anglican priesthood, but in 1880 his father died and Sinclair needed to earn a living immediately. He became the first cathedral organist of the new diocese of Truro. He moved from Truro to become organist of Hereford Cathedral in 1889, where he remained for the rest of his life.
At Hereford, Sinclair was conductor of eight Three Choirs Festivals between 1891 and 1912, working with leading British musicians of the day, including Edward Elgar, who incorporated into his Enigma Variations a portrait of Sinclair and his bulldog.
Sinclair was born in Croydon, the son of Dr R S Sinclair, director of public education in Bombay. The family had Irish connections, and at the age of eight, Sinclair entered the Royal Irish Academy of Music in Dublin. In 1873, aged ten, he gained a choral scholarship at St. Michael's College, Tenbury, under the headship of Sir Frederick Ouseley. He remained there for six years, singing in the choir at the daily services and deputising as organist.
1879 Sinclair became assistant organist to Charles Harford Lloyd at Gloucester Cathedral and parish organist of St Mary-de-Crypt, Gloucester. It had been expected that he would become an Anglican priest, but when he was seventeen his father died, and Sinclair was obliged to earn an income at once. In 1880, Edward White Benson, first Bishop of Truro, asked Ouseley for advice on a suitable organist for the new Truro Cathedral. Ouseley recommended Sinclair, who was appointed, aged 17. He designed a high-specification four-manual organ built by Father Willis, and assembled and trained a choir.