"Cassy O'" is a song by British singer-songwriter George Ezra.

It was released as the third single from his debut studio album Wanted on Voyage (2014).

The song was released in the United Kingdom as a digital download on 7 March 2014 through Columbia Records.

"Cassy O'" was re-released on 23 February 2015 to co-incide with Ezra's performance at the 2015 Brit Awards[1] and has since peaked at number 70 on the UK Singles Chart.

[3] In an interview with The Student Pocket Guide, when asked about the concept behind the video, Ezra said, "The whole point was to get as many Os, circle shapes, in one video.