Olivia Rose Olson is an American singer-songwriter, actress, and writer, largely known for her voice roles as Vanessa Doofenshmirtz in Phineas and Ferb and Marceline the Vampire Queen in Adventure Time. She also played the character of Joanna in the 2003 film Love Actually and its 2017 short sequel Red Nose Day Actually. Along with this, she is also a writer, having written the Boom! Studios graphic novel Marcy and Simon, co-authored Adventure Time: The Enchiridion and Marcy's Super-Secret Scrapbook, and contributed writing to the best-seller Adventure Time Encyclopedia' for Cartoon Network.

Voice actor and singer best known for her unforgettable appearance in the film Love Actually, singing "All I Want For Christmas". She went on to release the EP Beauty is Chaos. Her self-titled YouTube channel, where she publishes travel vlogs and singing performances, is also well-known.