Winstone, who is an actor, was unmasked as Firework in a double elimination alongside Doughnuts.
Her credits include films Donkey Punch and Kidulthood. She is also the daughter of Ray Winstone.
After being eliminated from the series, Winstone revealed she decided to participate for her five-year-old child, who she said was watching at home.
She also said the acting industry has been “very doom and gloom” over the past few years due to the pandemic, suggesting that she’s missed performing.
Winstone told ITV: “I usually take on roles that are very gritty and serious, so for me this was a great way to show people what I can do, what I love doing and to make my son very happy. He’s going to think his mummy is a firework. This was my main reason.”
Speaking about performing in front of Ora, she said: “Rita actually guessed me once but convinced herself that I would never do this show.”
The episode also saw all eight remaining contestants perform together for the second time.
Last week featured the unmasking of this series’ fifth contestant, Poodle, who was revealed to be Keane singer Tom Chaplin.
The Masked Singer continues next Saturday at 7pm on ITV.