The actress wished her "20s goodbye" by filming Queen Victoria's coronation for the new ITV drama, in which she stars as the monarch herself.
The brunette beauty shared a behind-the-scenes picture on Instagram as her character ascended to the throne.
Dressed in a golden robe, Jenna was seen on the red carpet while her tresses were styled into a neat up 'do.
"Snapped in the act #coronationday @official_itvvictoria @mammothscreen," the TV star captioned the photo.
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Jenna had earlier taken to Twitter to thank her fans for their messages on her big day, writing: "Goodbye 20s. Hello 30s. Feeling humbled. Birthday love."
Meanwhile, the official Queen Victoria account posted a nice message for their main star, adding: "Happy birthday to our Royal Majesty, @jenna_coleman_!"
The eight-part drama will follow the early life of the monarch, starting with her ascension to the throne at the age of 18.
Victoria teaser trailer
Victoria also stars Tom Hughes as Prince Albert and Eve Myles, among a stellar line-up.
Jenna's 30th comes just days after her Doctor Who replacement was announced ahead of 10th series of the reboot.
Little-known actress Pearl Mackie will play Peter Capaldi's on-screen companion Bill from next year.