Ashton Fletcher Irwin (born 7 July 1994) is an Australian musician, best known as the drummer of the pop rock band 5 Seconds of Summer.

[8] Irwin helped raise his younger siblings, half-brother Harry and half-sister Lauren, whilst attending Richmond High School, from which he graduated in 2012.

[9] During his high school years, prior to the formation of 5 Seconds of Summer, Irwin formed a jazz-funk band called "Swallow the Goldfish" with his classmates.

[6][10] Ultimately departing from the band, Irwin pursued a year of higher education at a TAFE college, studying music, before choosing to leave due to his commitment to 5 Seconds of Summer.

Irwin agreed, eventually joining the trio in posting song covers on Hemmings' YouTube channel, and forming the 5 Seconds of Summer lineup.

It was preceded by the single, "Straight to Your Heart", the track was described as an ’80s new wave-influenced alt-pop anthem, and was co-written and produced by Irwin in collaboration with John Feldmann.

[23] During the band's 2019 tour, Irwin documented, via his social media accounts, ice baths he partook in before each show as an affirmation of overcoming his substance abuse.