Written by Van Morrison and first recorded by Them (1964).
Hit versions by Them (US #93/UK #10 1965), The Shadows of Knight (US #10 1966), Van Morrison & John Lee Hooker (UK #31 1993).
http://youtu.be/FLvBpnaVHE8
From the wiki: “Van Morrison said that he wrote ‘Gloria’ while he performed with the Monarchs in Germany in the summer of 1963. He started to perform it at the Maritime Hotel when he returned to Belfast and joined up with The Gamblers to form the band Them. He would ad-lib lyrics as he performed, sometimes stretching the song to fifteen or twenty minutes. After signing a contract with Dick Rowe and Decca, Them went to London for a recording session at Decca Three Studios in West Hampstead on 5 July 1964.