Kristin Scott Thomas was born in Cornwall. Her father was a pilot for the Royal Navy and died in a flying accident in 1964. Scott Thomas's childhood home was Dorset, England. Her mother remarried another Royal Navy pilot, who also died in a flying accident six years after the death of her father. Scott Thomas was educated at Cheltenham Ladies' College and St Antony's Leweston School for Girls, in Dorset, and on graduation attended drama college. But on being told she would never be a good enough actor, she left at the age of 19 to work as an au pair in Paris.

Speaking French fluently, she studied acting at the École nationale supérieure des arts et techniques de théâtre (ENSATT) in Paris, and on graduation was cast opposite pop star Prince as the French girl in the film Under the Cherry Moon.

Kristin Scott Thomas was given an OBE in the 2003 Queen's Birthday Honours list, and was also awarded the Légion d'honneur by the French government in 2005. She has also played in many TV movies, and as an actress in the theatre.