Actors/Actresses:
* Olivia Colman: British actress known for her roles in "The Crown," "The Favourite," and "Fleabag."
* Oprah Winfrey: American talk show host, actress, producer, and philanthropist.
* Oscar Isaac: American actor known for his roles in "Star Wars: The Force Awakens" and "Ex Machina."
* Orlando Bloom: British actor known for his roles in "The Lord of the Rings" and "Pirates of the Caribbean."
* Octavia Spencer: American actress known for her roles in "The Help," "Hidden Figures," and "The Shape of Water."
* Owen Wilson: American actor known for his roles in "Wedding Crashers" and "The Royal Tenenbaums."
Musicians:
* Ozzy Osbourne: English singer and songwriter, known as the lead vocalist of Black Sabbath.
* Olivia Rodrigo: American singer and songwriter known for her hit songs "Drivers License" and "Good 4 U."
* One Direction: A popular English-Irish boy band.
* Olly Murs: English singer and songwriter known for his hit songs "Heart Skips a Beat" and "Troublemaker."
Athletes:
* Oscar Pistorius: South African Paralympic sprinter.
* Ole Gunnar Solskjaer: Norwegian former footballer and current manager of Manchester United.
* Oscar Robertson: American former professional basketball player, often considered one of the greatest point guards of all time.
Writers:
* Oscar Wilde: Irish poet and playwright known for his wit and literary works.
* Oliver Sacks: British neurologist and author known for his works on the human brain and consciousness.
* Orson Scott Card: American science fiction writer best known for his novel "Ender's Game."
Politicians:
* Otto von Bismarck: German statesman known as the "Iron Chancellor" for unifying Germany.
* Olaf Scholz: Current Chancellor of Germany.
Other:
* Oprah's Angel Network: A charitable organization founded by Oprah Winfrey.
* Oscar Awards: The annual awards ceremony honoring excellence in cinematic achievements.
This is just a small sample of famous people with first names starting with "O." There are many others, in a wide variety of fields.