O
- Austin O'Brien (born 1981)
- Last Action Hero (1993) - as Danny
- My Girl 2 (1994) - as Nick
- Promised Land (1996–1999)
- Margaret O'Brien (born 1937)
- Babes on Broadway (1941)
- Journey for Margaret (1942)
- Lost Angel (1943)
- Music for Millions (1944)
- The Canterville Ghost (1944)
- Jane Eyre (1944)
- Meet Me in St. Louis (1944)
- Our Vines Have Tender Grapes (1945)
- Three Wise Fools (1946)
- Bad Bascomb (1946)
- Big City (1948)
- Tenth Avenue Angel (1948)
- The Secret Garden (1949)
- Little Women (1949)
- Her First Romance (1951)
- Tatum O'Neal (born 1963)
- Paper Moon (1973)
- The Bad News Bears (1976)
- Nickelodeon (1976)
- International Velvet (1978)
- Little Darlings (1980)
- Heather O'Rourke (1975–1988)
- Poltergeist series (1982–88) - as Carol Anne Freeling
- Happy Days (1982–1983)
- Ethelmary Oakland (1909–1999)
- The Dummy (1917)
- Divorce and the Daughter (1916)
- The World and the Woman (1916)
- The Shine Girl (1916)
- John Brewster's Wife (1916)
- Hearts of Men (1915)
- Always in the Way (1915)
- Georg Olden (1968)
- How to Eat Like a Child (1981)
- ABC Weekend Special: The Joke's on Mr. Little (1982)
- Bad Manners (aka: Growing Pains) (1984)
- Explorers (1985)
- Rocky Road (1985–1987)
- Barret Oliver (born 1971)
- Jekyll and Hyde... Together Again (1982)
- Uncommon Valor (1983)
- The NeverEnding Story (1984)
- Cocoon (1985)
- D.A.R.Y.L. (1985)
- Spot Marks the X (1986)
- The Secret Garden (1987)
- Cocoon: The Return (1988)
- Scenes from the Class Struggle in Beverly Hills (1989)
- Tony Oller (born 1991)
- As the Bell Rings (2007–present)
- Elizabeth Olsen (born 1989)
- How the West Was Fun (1994)
- The Adventures of Mary-Kate & Ashley: The Case of the Mystery Cruise (1995)
- Mary-Kate and Ashley Olsen aka as The Olsen Twins (born 1986)
- Full House (1987–1995) - as Michelle Tanner
- To Grandmother's House We Go (1992) - as Julie and Sarah Thompson
- The Little Rascals (1994) - as Themselves
- It Takes Two (1995) - as Amanda Lemmon and Alyssa Callaway
- Two of a Kind (1998–1999)
- Billboard Dad (1998) - as Tess and Emily Tyler
- Passport to Paris (1999) - as Melanie and Allyson Porter
- Switching Goals (1999) - as Emma and Sam Stanton
- Winning London (2001) - as Chloe and Riley Lawrence
- When in Rome (2002) - as Charli and Leila
- Susan Olsen (born 1961)
- The Brady Bunch (1969–1974) - as Cindy Brady
- The Brady Kids (1972–1974) (voice)
- Renee Olstead (born 1989)
- Streets of Laredo (1995)
- Deadly Family Secrets (1995)
- Ceftin Wiz Kids (1996)
- Santa, NASA & the Man in the Moon (1996)
- Cadillac Ranch (1996)
- Out There (1997)
- The Usher (1997)
- Reunited (1998)
- The Insider (1999)
- End of Days (1999)
- Geppetto (2000)
- Space Cowboys (2000)
- Scorched (2003)
- 13 Going on 30 (2004)
- Still Standing (2002–2006)
- Drew Osborne (born 1991)
- Stop That Cycle (2004)
- Piggybanks (2004)
- UnderCover Kids (2004)
- Hannah Montana (2006)
- Vicious Circle (2008)
- Emily Jordan Osment (born 1992)
- The Secret Life of Girls (1999)
- Sarah, Plain and Tall: Winter's End (1999)
- 3rd Rock from the Sun (1999)
- Edwurd Fudwupper Fibbed Big (2000)
- Touched by an Angel (2000)
- Friends (2001)
- Spy Kids 2: Island of Lost Dreams (2002)
- Spy Kids 3-D: Game Over (2003)
- Hannah Montana (2006–2011)
- The Haunting Hour: Don't Think About It (2007)
- Soccer Mom (2008)
- Dadnapped (2009)
- Hannah Montana: The Movie (2009)
- Haley Joel Osment (born 1988)
- Forrest Gump (1994)
- The Jeff Foxworthy Show (1995–1997)
- Bogus (1996)
- Murphy Brown (1997–1998)
- The Sixth Sense (1999) - as Cole Sear
- Pay It Forward (2000) - as Trevor McKinney
- AI: Artificial Intelligence (2001)
- The Jungle Book 2 (2003) (voice)
- Secondhand Lions (2003)
- Peter Ostrum (born 1957)
- Willy Wonka & the Chocolate Factory (1971)
Read more about this topic: List Of Former Child Actors From The United States