Steve Marriner, also known as Steve Gregg, (born 1984 in Ottawa, Ontario) is a Canadian multi-instrumentalist, singer, songwriter and record producer based in Ottawa, Ontario. He first garnered attention in the Ottawa blues scene in his early teens as a prodigy blues harp (harmonica) player. He also plays baritone guitar, electric guitar, piano, Hammond organ, upright bass and electric bass). As of 2016, he is the frontman, singer, one of two guitarists and harmonica player for the Canadian rock'n'roll-blues group MonkeyJunk. The band's album To Behold won the 2011 Juno Award for Blues Album of the Year. Prior to forming MonkeyJunk, Marriner was a member of two Ottawa bands, the Johnny Russell Band and the JW-Jones Blues Band. He appeared several times on the mainstage of the Ottawa Bluesfest as a member of the JW-Jones Blues Band.
Marriner began playing the harmonica at eleven years of age. He first studied the harmonica with Ottawa-based bluesman Larry "The Bird" Mootham. After a year of tutelage, Marriner began joining The Bird and his band on stage in Ottawa-area clubs. Before taking the stage for the first time, Marriner was bestowed with the moniker "Southside Steve," a reference to his home on the South end of Ottawa. This stage name was used for the next several years.
In the summer of 1998, at the age of thirteen, "Southside Steve" met guitarist Tony D, (Tony Diteodoro) and would perform regularly with him at The Rainbow Bistro. The two would later form MonkeyJunk with drummer Matt Sobb in 2008.
Later in 1998, Marriner joined The Johnny Russell Band. The band played Chicago Blues and New Orleans music and performed around the provinces of Ontario and Quebec.