"Eighth Day" is a song by British singer-songwriter Hazel O'Connor, released in August 1980 as the second single from her debut and soundtrack album, Breaking Glass.

[2] O'Connor wrote the song twelve hours before it was recorded as a parallel story of the Book of Genesis where Man made the Earth in his own image, and "having unleashed elements he cannot control, the Man-made Machine Monster takes over".

[3] Writing in Record Mirror, Simon Ludgate described the song as "the worst track from the album" with its release "something to do with a strong visual appeal because of the accompanying film clip".

He said it "sounds like a latter-day 'Messiah'" and that "Monsters in Disguise" should have been released as a single instead.

However, in the same magazine issue, reviewer Gill Pringle said "I'm impressed.