Mary Hopkin (born 3 May 1950), credited on some recordings as Mary Visconti from her marriage to Tony Visconti, is a Welsh singer best known for her 1968 UK number one single "Those Were the Days". She was one of the first artists to be signed to the Beatles' Apple label.

Mary Elizabeth Blodwen Hopkin was born into a Welsh-speaking family in Pontardawe, Glamorgan, Wales. She took weekly singing lessons as a child and began her musical career as a folk singer with a local group called the Selby Set and Mary. She released an EP of Welsh-language songs for a local record label called Cambrian, based in her hometown, before signing to Apple Records, owned by the Beatles, one of the first artists to do so. The model Twiggy saw her winning the ITV television talent show Opportunity Knocks and recommended her to Paul McCartney.

Hopkin's debut single, "Those Were the Days", produced by McCartney, was released in the UK on 30 August 1968. Despite competition from well-established star Sandie Shaw, whose own single version of the song was also released that year, Hopkin's version became a number one hit on the UK singles chart. It reached number two on the US Billboard Hot 100, where for three weeks it was held out of the top spot by the Beatles' "Hey Jude", and spent two weeks at number one on Canada's RPM singles chart. It sold over 1,500,000 copies in the United States alone, and was awarded a gold disc by the RIAA. Global sales topped 8,000,000. Hopkin's recording of "Those Were The Days" was nominated for the "Best Contemporary Pop Vocal Performance, Female" at the 11th Annual Grammy Awards in March 1969.

On 2 October 1968, Hopkin appeared at St Paul's Cathedral in London for the Pop Experience, where she sang "Morning of My Life", "Turn Turn Turn", and "Plaisir d'amour". In December that year, the NME music magazine reported that Hopkin was considering a lead acting role in Stanley Baker's planned film Rape of the Fair Country, which was to be based on Alexander Cordell's book of the same name. That particular project did not materialise but Hopkin did sing the title songs to two of Baker's films, Where's Jack? and Kidnapped.

On 21 February 1969, Hopkin's debut album, Post Card, again produced by McCartney, was released. It included covers of three songs from Donovan, who also played on the album, and one song each from George Martin and Harry Nilsson. It reached number three on the UK Albums Chart, although it proved to be her solitary success in that chart. In the United States, Post Card reached number 28 on the Billboard albums chart.

The next single was "Goodbye", written by McCartney (credited to Lennon–McCartney), and released on 26 March 1969. It reached number two on the UK singles chart, number 13 on the Billboard Hot 100 and number 15 on the RPM chart in Canada. Hopkin said she interpreted "Goodbye" as McCartney pledging to stop "micromanaging" her career, since she was uncomfortable with his positioning of her as a pop chanteuse. She also expressed dissatisfaction with her manager at this time, Terry Doran.

Hopkin's third single, "Temma Harbour", was a re-arrangement of a Philamore Lincoln song. Her first single not to be produced by McCartney, it was released on 16 January 1970 and peaked at number six in the UK and number 42 in Canada. In the US, "Temma Harbour" reached number 39 on the Billboard Hot 100 and number four on the magazine's Easy Listening chart. Along with Donovan and Billy Preston, Hopkin was one of the chorus singers on the Radha Krishna Temple's 1970 hit single "Govinda", produced by George Harrison for Apple Records.

In March 1970, Hopkin represented the United Kingdom in the 1970 Eurovision Song Contest, achieving second place with "Knock, Knock Who's There?" Despite being the pre-contest favourite, Hopkin lost to "All Kinds of Everything", performed by Irish singer Dana. Produced by Mickie Most, "Knock, Knock Who's There?" was released as a single on 23 March 1970 and peaked at number two in the UK. It was a worldwide hit, selling over a million.^{[citation needed]}