Gordon Trueman Riviere Waller (4 June 1945 – 17 July 2009) was a Scottish guitarist, singer-songwriter and actor, best known as Gordon of the 1960s pop music duo Peter and Gordon, whose biggest hit was the no. 1 million-selling single "A World Without Love".

Waller was born in Braemar, Aberdeenshire, Scotland, the son of a prominent surgeon who was based in Pinner. His family lived in London, England, but his mother moved to Scotland to give birth to him, as the Second World War was still happening. When Waller was a small child, the family moved to Middlesex, where he gained entrance to Westminster School.

While attending Westminster School he met fellow student Peter Asher, likewise the son of a doctor, in 1959 and they began playing together as a duo – Peter and Gordon. Asher mentioned in a 2006 interview that "Our voices are quite different, Gordon's and mine, but we tried singing together experimentally and we found that we could achieve this very nice harmony."

They secured a two-week residency at The Pickwick Club, owned by Harry Secombe, while Asher was studying philosophy at university and Waller was still at boarding school. Every evening, Gordon would sneak out of boarding school by climbing over the school gates to attend the gig, however one night he stabbed the bottom of his foot on the gates spikes, permanently damaging it (Waller said in an interview in the 2000s that a hole was still there). Through Secombe, they met Norman Newell, who signed them to EMI.

Asher is the elder brother of actress and businesswoman Jane Asher, who in the mid-1960s was girlfriend of the Beatles' Paul McCartney. Through this connection he and Waller were given unrecorded Lennon–McCartney songs to perform, most notably the duo's first and biggest hit, "A World Without Love" (1964), which went to number one in both the UK and US. The duo were one of the most popular acts to come to America from the UK as a part of the British Invasion.

Peter and Gordon disbanded in 1968. Waller described the duo parting ways: "We just decided we'd done what we could do at the time. In those days, even if you were top of the bill, you only did like 20 to 25 minutes. By about '67, '68, that 25 minutes was just taken up with playing hits. So we didn't have time for anything other than the hits. It just got very, very tedious doing the same songs night after night after night. So we said let's give it a break for a bit and concentrate on recording."

Peter and Gordon reunited for a benefit concert in 2005 for Mike Smith of The Dave Clark Five. From then onwards the two would reunite a few more times. On 19 July 2008, Peter and Gordon performed together at The Cannery Casino in Las Vegas, Nevada. Also on the bill that night were Chad & Jeremy. Both duos sang the final concert song ("Bye Bye Love") together for only the second time. On 21 August 2008, they performed a free concert on the pier in Santa Monica, California, briefly accompanied by Joan Baez. On 2 February 2009 Gordon performed with Asher at the Surf Ballroom as part of a tribute concert marking the 50th anniversary of "the Day the Music Died".

With Waller and Asher parting ways, Waller attempted a solo career with little success, releasing one record, ...and Gordon. He also appeared in a production of Joseph and the Amazing Technicolor Dreamcoat as Pharaoh in 1971, a performance that he reprised on the LP. Waller first performed "Joseph" at the Edinburgh Festival, later reprising the role at the Albery Theatre in London's West End.