The 25-year-old actor – who played Princess Diana in the most recent series of the Netflix royal drama – hinted they are realigning their gender identity as they discussed embracing change and a new journey.
Corrin has changed the pronouns on the bio of their Instagram account to "she/they", implying they identify as both. The they pronoun is used by those who identify as non-binary.
They shared an image of their chest bound with boxing tape and captioned it: "Some time before I bought my first binder, messing around with @sirdavidsimon, we used boxing wrap, thanks for capturing this with me, very intimate, very new, very cool. It’s all a journey right. Lots of twists and turns and change and that’s ok! Embrace it."
Corrin also revealed they use g2cb binders – an LGBT brand.
Chest binding or breast binding is the act of flattening the chest using constrictive fabric.
The Pennyworth star recently identified themself as "queer" on social media.
Sharing a picture of themself in a wedding dress from a photoshoot for Pop magazine they captioned it "ur fave queer bride".
Corrin is currently the face of women's fashion brand Mui Mui's spring/summer 2021 campaign.
In May they were spotted filming alongside One Direction's Harry Styles in Brighton, who they are starring with in the upcoming film My Policeman.
Styles, 27, is playing the titular police officer in the adaption of Bethan Robert's 2012 novel, while Corrin takes the role of his on-screen wife Marion.
Corrin has shot to fame since being cast in The Crown, winning a Critic's Choice and Golden Globe award as well as numerous other nominations for their performance.
They attended an all-girls Catholic boarding school before studying drama at Bristol and Cambridge universities.
Yahoo UK has contacted a representative for Corrin for comment.
Watch: Emma Corrin and Harry Styles filming My Policeman in Brighton