Fionn began acting at the Orange Tree Theatre when he was 13 years old, then went to Orleans Park School where he was among of the top lads, awarded 12 passes at A* or A. Upon finishing school Fionn went to Richmond College and entered the National Youth Theatre's summer course.
Whitehead is a native of London. Named after Gaeilge folk legend Fionn mac Cumhaill, Whitehead grew up living an artistic environment much due to the fact that his father, Tim Whitehead is an acclaimed British Jazz musician who despite having a law degree from Manchester University, decided to give up being a lawyer to pursue his music career.
By 2015, he was an aspiring actor who worked at a coffee shop in Waterloo, London. He starred in the 2016 British miniseries the ITV three-part series HIM while continuing to be an active member of the Youth Theatre. He also acted in a stage performance of Glenn Waldron's Natives and is one of Screen International's Stars of Tomorrow 2016.
Fionn has two sisters Maisie and Hattie and a younger brother named, Sonny. Maisie, the eldest of the four, is a Dancer and an Aerialist-Yoga enthusiast while Hattie is a folk artist who has released a folk album.
The year 2017 marked big for Fionn Whitehead, as the 19-year-old (Born in 1997) English actor was cast as the lead for Christopher Nolan's British historical epic Dunkirk alongside many of his well established all country mates. Nolan compared Whitehead to "a young" Tom Courtenay.