Millie Alcock is a 26-year-old Australian actress from Sydney who became known around the world as the young Rhaenyra Targaryen in HBO’s House of the Dragon. Born on April 11, 2000, she built her career in Australian television before landing the role that made her a global name, and she has since been cast as Supergirl in the DC Universe.
Quick Facts
| Full Name | Millie Alcock |
| Age | 26 years old |
| Date of Birth | April 11, 2000 |
| Birthplace | Sydney, New South Wales, Australia |
| Nationality | Australian |
| Height | 5 ft 5 in (1.65 m) |
| Occupation | Actress |
| Known For | House of the Dragon, Upright, Sirens, Supergirl |
| Years Active | 2014–present |
Who Is Millie Alcock?
Millie Alcock is an Australian actress best known for playing the young Princess Rhaenyra Targaryen in the first season of HBO’s Game of Thrones prequel House of the Dragon. She appeared in the opening five episodes of the series in 2022, portraying Rhaenyra as a teenager and young woman before the role passed to Emma D’Arcy for the character’s adult years. Her performance was widely praised and turned her into one of the most talked-about young actors of the year.
Before House of the Dragon, Alcock had already made her name at home in Australia with the Foxtel drama Upright, in which she starred opposite Tim Minchin as Meg, a runaway teenager on a road trip across the Australian outback. The role showed off the natural, unforced screen presence that would later win over international audiences. In 2025 she starred as Simone DeWitt in the Netflix limited series Sirens, alongside Julianne Moore and Meghann Fahy, and she has been cast as Kara Zor-El, better known as Supergirl, in James Gunn’s new DC Universe.
Early Life & Background
Millie Alcock was born on April 11, 2000, in Sydney, New South Wales, Australia, where she grew up. She attended Newtown High School of the Performing Arts in Sydney, a school known for nurturing young creative talent. As a teenager she began working in commercials and short films, picking up small television roles while still at school.
Her early screen credits included an appearance in the Australian drama Wonderland in 2014 and a role in the Netflix and ABC co-production Pine Gap in 2018, in which she played Marissa Campbell. She also appeared in the crime drama Reckoning in 2019 and the Stan series The Gloaming in 2020. Those parts gave her steady experience in front of the camera and led to her first leading role in Upright, which began airing in 2019 and ran for two seasons.
Career
Alcock’s breakthrough came with Upright, the Australian comedy-drama in which she played Meg, a teenager who crosses paths with a down-on-his-luck musician played by Tim Minchin. The series was a hit in Australia and earned her a strong following at home. It also put her on the radar of international casting directors looking for fresh talent.
In 2022 she joined House of the Dragon as the young Rhaenyra Targaryen, the daughter of King Viserys I and heir to the Iron Throne. Alcock played Rhaenyra in the first five episodes of the first season, capturing the character’s confidence, ambition and vulnerability. Her performance earned widespread critical praise and made her one of the breakout stars of the series, even though her time on the show was brief by design, with the story jumping forward in time after episode five.
After House of the Dragon, Alcock moved into major international projects. In January 2024 she was announced as the new Supergirl, cast as Kara Zor-El in James Gunn’s DC Universe. She made a brief first appearance as the character in Superman in 2025, ahead of her own standalone film Supergirl, which is scheduled for release in 2026. She also starred in the Netflix limited series Sirens in 2025, playing Simone DeWitt, the devoted assistant to a wealthy socialite played by Julianne Moore.
Facts About Millie Alcock
- She attended Newtown High School of the Performing Arts in Sydney.
- She landed her breakout Australian role as Meg in Upright before House of the Dragon.
- She played the younger Rhaenyra Targaryen in the first five episodes of House of the Dragon.
- She was cast as Supergirl in James Gunn’s DC Universe in January 2024.
- She starred as Simone DeWitt in Netflix’s Sirens (2025) alongside Julianne Moore.
Frequently Asked Questions
How old is Millie Alcock?
Millie Alcock is 26 years old. She was born on April 11, 2000, in Sydney, Australia.
How tall is Millie Alcock?
Millie Alcock is 5 ft 5 in (1.65 m) tall.
Who did Millie Alcock play in House of the Dragon?
Millie Alcock played the young Princess Rhaenyra Targaryen in the first five episodes of House of the Dragon season 1. Emma D’Arcy plays the adult Rhaenyra in later episodes.
Is Millie Alcock playing Supergirl?
Yes. Millie Alcock was cast as Kara Zor-El, also known as Supergirl, in James Gunn’s DC Universe. She made a brief appearance as the character in Superman (2025), and her standalone film Supergirl is scheduled for release in 2026.
Where is Millie Alcock from?
Millie Alcock is from Sydney, New South Wales, Australia, where she was born and raised.
How old is Millie Alcock?
Millie Alcock is 26 years old. She was born on April 11, 2000, in Sydney, Australia.
How tall is Millie Alcock?
Millie Alcock is 5 ft 5 in (1.65 m) tall.
Who did Millie Alcock play in House of the Dragon?
Millie Alcock played the young Princess Rhaenyra Targaryen in the first five episodes of House of the Dragon season 1. Emma D’Arcy plays the adult Rhaenyra in later episodes.
Is Millie Alcock playing Supergirl?
Yes. Millie Alcock was cast as Kara Zor-El, also known as Supergirl, in James Gunn’s DC Universe. She made a brief appearance as the character in Superman (2025), and her standalone film Supergirl is scheduled for release in 2026.
Where is Millie Alcock from?
Millie Alcock is from Sydney, New South Wales, Australia, where she was born and raised.
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