Lady Gaga joined U2 on stage at Madison Square Garden last night (26 July) to perform 'Ordinary Love'. Watch it below.

The singer surprised fans by climbing up onto the NYC stage partway through the band's eight-show run at Madison Square Garden, as Bono introduced her: "Her Lady-ness, her Gaga-ness is here this evening. It's a treat."

Taking to the piano, Gaga joined Bono for a slightly strained rendition of 'Ordinary Love', which was U2's contribution to the Mandela: Long Walk To Freedom soundtrack, and was released less than a week before Nelson Mandela died.

Watch U2 and Lady Gaga perform 'Ordinary Love' below

The song was nominated for an Academy Award for Best Original Song, and also won a Golden Globe in the same category.

Meanwhile, U2 are set to embark on a five-night residency at London's O2 Arena in October, followed by two nights at Glasgow's SSE Hydro. See full UK tour dates below. For tickets and more information, click here.

Sun October 25 2015 - London O2 Arena
Mon October 26 2015 - London O2 Arena
Thu October 29 2015 - London O2 Arena
Fri October 30 2015 - London O2 Arena
Mon November 02 2015 - London O2 Arena

Fri November 06 2015 - Glasgow SSE Hydro
Sat November 07 2015 - Glasgow SSE Hydro