Milly Alcock

Milly Alcock grew up in Petersham, a suburb of Sydney, with her mother, Emma Alcock, and two younger brothers. She has described herself as the only artistic member of her immediate family and said that the arts gave her a sense of independence. Before filming House of the Dragon, she worked part time at a café in Marrickville, where she continued washing dishes until production began.

Alcock moved to London in 2022. In 2026, she disclosed that she had been diagnosed with attention deficit hyperactivity disorder.

Alcock was introduced to acting as Little Red Riding Hood in her primary school's production of Little Red Rocking Hood. She switched to Newtown High School of the Performing Arts at 13 and found an agent by contacting agencies herself. Her first professional screen appearance came as an extra in the television series Wonderland in 2014.

She later presented the Disney Channel Australia short-form programmes B.F. Chefs and Hanging With. Her early named roles included Isabella Barrett in the web miniseries High Life and Cindi Jackson in Janet King. She also appeared in A Place to Call Home, Fighting Season, Pine Gap, Les Norton and the feature film The School.

In 2018, Alcock left Newtown High School of the Performing Arts after being cast as Meg Adams in Tim Minchin's Foxtel comedy-drama Upright. The series follows Meg, a runaway teenager who hitchhikes across 3,200 kilometres of the Australian outback. Alcock returned for the second series in 2022.

Her performance brought a nomination for Best Comedy Performer at the 10th AACTA Awards, making her one of the youngest nominees in the category. She also received the Casting Guild of Australia's Rising Star Award in 2018. Her other television work from this period included The Gloaming and Reckoning.

Alcock was cast as young Princess Rhaenyra Targaryen in HBO's House of the Dragon, the prequel to Game of Thrones. She appeared in the first season as a main cast member and returned for a guest appearance in the second season, with Emma D'Arcy playing the older Rhaenyra. Alcock's performance drew critical acclaim and earned a Critics' Choice Television Award nomination for Best Supporting Actress in a Drama Series.

Because she had not previously worked on a medieval period drama, Alcock looked to Cate Blanchett's performance in Elizabeth: The Golden Age when developing Rhaenyra's physical bearing and mannerisms. During production, she became close with co-stars Paddy Considine and Rhys Ifans, who played King Viserys I Targaryen and Otto Hightower. They introduced her to the Australian punk band Amyl and the Sniffers.

In 2024, Alcock was cast as Kara Zor-El, also known as Supergirl, in the DC Universe. She first appeared uncredited as the character in Superman in 2025 before starring in Supergirl in 2026. She is set to reprise the role in Man of Tomorrow.

Alcock also starred as Simone DeWitt in the Netflix limited series Sirens and made her West End debut as Abigail Williams in The Crucible at London's Gielgud Theatre in 2023. Her other screen appearances include the short films Furlough, The Familiars and Based Amy, on which she was also an executive producer. She appeared in the 2023 music video for Noel Gallagher's High Flying Birds' song "Easy Now."