| The O.C. | Fox | 2003–2007 | 4 | 92 | LGBTQ |
| O Canada | Cartoon Network | 1997–2002 | — | — | Anthology |
| O'Grady | TeenNick | 2004–2006 | 2 | 19 | — |
| O'Hara, U.S. Treasury | CBS | 1971–1972 | 1 | 22 | Police procedural |
| The O'Reilly Report | Fox News | 1996–2017 | 17 | 5,321 | Current affairs show |
| O2Be | Oxygen | 2002 | 1 | 6 | Comedy |
| The OAWeb series | Netflix | 2016–2019 | 2 | 16 | Fantasy |
| The Oath | Crackle | 2018–2019 | 2 | 10 | Drama |
| Obi-Wan Kenobi | Disney+ | 2022 | 1 | 6 | Science fiction |
| Obliterated | Netflix | 2023 | — | — | Action |
| The OblongsAnimated series | The WB | 2001–2002 | 1 | 13 | Comedy |
| Obsessed | A&E | 2009–2010 | 2 | 17 | Reality |
| Occasional Wife | NBC | 1966–1967 | 1 | 30 | Sitcom |
| The OCD Project | VH1 | 2010 | 1 | 8 | Reality |
| Ocean Ave. | TV4 | 2002–2003 | 1 | 146 | — |
| Ocean Force | TruTV | 2007 | 6 | 42 | Reality |
| Ochocinco: The Ultimate Catch | VH1 | 2010 | 1 | 10 | Reality |
| October Faction | Netflix | 2020 | 1 | 10 | Fantasy |
| October Road | ABC | 2007–2008 | 2 | 19 | Drama |
| The Odd Couple | ABC | 1970–1975 | 5 | 114 | Sitcom |
| The Odd Couple | CBS | 2015–2017 | 2 | 12 | Sitcom |
| Odd Man Out | ABC | 1999–2000 | 1 | 13 | Teen sitcom |
| Odd Mom Out | Bravo | 2015–2017 | 3 | 30 | Sitcom |
| Odd Squad | PBS, PBS Kids | 2014–2022 | 3 | 108 | Educational entertainment |
| The Oddball CoupleAnimated series | ABC | 1975 | 1 | 16 | Children's |
| OddballsAnimated series | Netflix | 2022–2023 | 2 | 20 | Adventure |
| Oddities | Discovery Channel | 2010–2014 | 4 | 46 | Reality |
| Oddville, MTV | MTV | 1997–1999 | — | 65 | Comedy |
| The OdysseyMiniseries | NBC | 1997 | — | 2 | Drama |
| Of Kings And Prophets | ABC | 2016 | 1 | 13 | — |
| The Off-BeatsAnimated series | Nickelodeon | 1996–1998 | 2 | 14 | Children's |
| Off Campus | Prime Video | 2026–on air | 1 | 8 | Romantic |
| Off Centre | The WB | 2001–2002 | 2 | 28 | Sitcom |
| Off Limits | Travel Channel | 2011–2013 | 3 | 30 | Documentary |
| Off Pitch | VH1 | 2013 | 1 | 8 | Reality |
| Off the Air | Adult Swim | 2011 | 5 | 27 | Anthology |
| Off the Hook: Extreme Catches | Animal Planet | 2012–2013 | 2 | 17 | Reality |
| Off the Map | ABC | 2011 | 1 | 13 | Drama |
| Off the Rack | ABC | 1984–1985 | 1 | 7 | Sitcom |
| Off the Wall | Disney Channel | 1998–1999 | — | — | Game show |
| The OfferMiniseries | Paramount+ | 2022 | — | 10 | Biographical |
| The Office | CBS | 1995 | 1 | 6 | Sitcom |
| The Office | NBC | 2005–2013 | 9 | 204 | Mockumentary |
| The Office: The Accountants | NBC | 2006 | 1 | 10 | Mockumentary |
| Oh Baby | Lifetime | 1998–2000 | 2 | 44 | Sitcom |
| Oh, Grow Up | ABC | 1999 | 1 | 13 | Sitcom |
| Oh Madeline | ABC | 1983–1984 | 1 | 19 | Sitcom |
| Oh Sit! | The CW | 2012–2013 | 2 | 20 | Game show |
| Oh! Those Bells | CBS | 1962 | 1 | 13 | Sitcom |
| Oh Yeah! CartoonsAnimated series | Nickelodeon | 1998–2013 | 4 | 75 | Anthology |
| Ohara | ABC | 1987–1988 | 2 | 30 | Detective |
| Oil Change | The Sports Network | 2010–2014 | 4 | 24 | Documentary |
| Ojo Por Ojo | Telemundo | 2010–2011 | — | 98 | Telenovela |
| OK K.O.! Let's Be HeroesAnimated series | Cartoon Network | 2017–2019 | 3 | 112 | Comedy |
| Okay, Mother | WNYW | 1948–1951 | 3 | — | Game show |
| Olaf Presents | Disney Channel | 2021–on air | 1 | 5 | Comedy |
| Olbermann | ESPN2 | 2013–2015 | — | 434 | — |
| The Old Man | FX | 2022–on air | 2 | 15 | — |
| The Old Man and the SeaMiniseries | | 1990 | — | — | Drama |
| Old Skool with Terry and Gita | VH1 | 2008–2009 | 1 | 5 | — |
| The Oldest Rookie | CBS | 1987–1988 | 1 | 14 | Detective |
| Olive KitteridgeMiniseries | HBO | 2014 | 1 | 4 | Drama |
| Oliver Beene | Fox | 2003–2004 | 2 | 24 | Sitcom |
| OliviaAnimated series | Nick Jr. | 2009–2013 | 2 | 37 | Comedy |
| The Ollie & Moon ShowAnimated series | Universal Kids/MeTV Toons, TVOKids | 2017–2018 | 1 | 52 | Comedy |
| Olympics on ABC | ESPN on ABC | 1964–1988 | 10 | — | — |
| Omba Mokomba | Disney Channel | 1997 | — | 27 | Nature documentary |
| Omnibus | CBS | 1952–1961 | 8 | 164 | Variety show |
| On Air with Ryan Seacrest | Syndication | 2004 | — | — | — |
| On Becoming a God in Central Florida | Showtime | 2019 | 1 | 10 | Black comedy |
| On Brand with Jimmy Fallon | NBC | 2025 | — | — | Reality competition |
| On Call | Prime Video | 2025–on air | 1 | 8 | Procedural |
| On Death Row | Channel 4 | 2012 | — | 4 | Documentary |
| On Location | HBO | 1975–1985 | — | 18 | Comedy |
| On My Block | Netflix | 2018–2021 | 4 | 38 | Coming-of-age |
| On Our Own | ABC | 1994–1995 | 1 | 20 | Sitcom |
| On Our Own (1977 TV series) | CBS | 1977–1978 | — | — | Sitcom |
| On Patrol: Live | Reelz | 2022–on air | — | — | Reality |
| On the Air | ABC | 1992 | 1 | 7 | Sitcom |
| On the Case with Paula ZahnNews program | Investigation Discovery | 2009 | 22 | 113 | — |
| On the Fly | TLC | 2012 | 1 | 13 | Reality |
| On the Lot | Fox | 2007 | 1 | 16 | Reality |
| On the Menu | TNT | 2014 | 1 | 10 | Reality |
| On the MoneyNews program | Syndication | 1970–2019 | — | — | Sunday morning talk show |
| On the MoneyNews program | CNBC | 2005–2009 | — | — | — |
| On the Record with Brit Hume | Fox News | 2002–2016 | — | — | Current affairs |
| On the Road with Austin & Santino | Lifetime | 2010 | 1 | 14 | Reality |
| On the Rocks | ABC | 1975–1976 | 1 | 24 | — |
| On the Spot | The WB | 2003 | 1 | 5 | Comedy |
| On the Spot | Syndication | 2011 | 4 | 33 | Reality |
| On the Team | Noggin | 2001 | 1 | 13 | — |
| On the Television | Nick at Nite | 1990–1991 | — | — | Comedy |
| On Wings of EaglesMiniseries | NBC | 1986 | — | 2 | Drama |
| Once a Hero | ABC | 1987 | 1 | 7 | Science fiction |
| Once an Eagle | NBC | 1976–1977 | 1 | 7 | Drama |
| Once and Again | ABC | 1999–2002 | 3 | 63 | Drama |
| Once Upon a Time | ABC | 2011–2018 | 7 | 155 | Drama |
| Once Upon a Time in Wonderland | ABC | 2013–2014 | 1 | 13 | Fantasy |
| Once Upon a Tune | DuMont | 1951 | — | — | — |
| One Big Family | Syndication | 1986–1987 | 1 | 25 | Sitcom |
| One Big Happy | NBC | 2015 | 1 | 6 | Comedy |
| One Big Happy Family | TLC | 2009–2010 | 2 | 10 | Reality |
| One Car Too Far | Discovery Channel | 2012 | — | 5 | Reality |
| One Day at a Time | CBS | 1975–1984 | 9 | 209 | Sitcom |
| One Day at a Time | Netflix | 2017–2019 | 4 | 46 | Sitcom |
| One Day at Disney | Disney+ | 2019–on air | 1 | 52 | Documentary |
| One Dollar | Paramount+ | 2018 | — | — | Thriller |
| One Happy Family | NBC | 1961 | 1 | 15 | Sitcom |
| One in a Million | ABC | 1980 | 1 | 13 | Sitcom |
| One Life to Live | ABC | 1968–2013 | 45 | 11,136 | Soap opera |
| One Man's Experience | DuMont | 1952–1953 | 1 | — | Anthology |
| One Minute Please | DuMont | 1954–1955 | — | — | Panel game |
| One Mississippi | Prime Video | 2015–2017 | 2 | 12 | Comedy-drama |
| One Nation with Brian Kilmeade | Fox News | 2022–on air | 3 | — | News |
| One Ocean View | ABC | 2006 | 1 | 2 | Reality |
| One of the Boys | NBC | 1982 | 1 | 13 | Sitcom |
| One of the Boys | NBC | 1989 | 1 | 6 | Sitcom |
| One of Us Is Lying | Peacock | 2021–2022 | 2 | 16 | Mystery |
| One on One | UPN | 2001–2006 | 5 | 113 | Teen sitcom |
| One Piece | Netflix | 2023–on air | 2 | 16 | Comedy |
| One Punk Under God | Sundance TV | 2006–2007 | 1 | 6 | Documentary |
| One to Grow On | NBC | 1983–1989 | — | — | — |
| One Tree Hill | The CW, The WB | 2003–2012 | 9 | 187 | Youth |
| One Way Out | Discovery Channel | 2007 | — | 8 | Reality |
| One West Waikiki | CBS | 1994–1996 | 2 | 20 | Crime |
| One Woman's Experience | DuMont | 1952–1953 | 1 | — | Anthology |
| One World | NBC | 1998–2001 | 3 | 39 | Sitcom |
| Oni: Thunder God's TaleAnimated series | | 2022–on air | 1 | 4 | Fantasy |
| Onion News Network | IFC | 2011 | 2 | 20 | Magazine format |
| Onion SportsDome | Comedy Central | 2011 | 1 | 10 | — |
| Online Dating Rituals of the American Male | Bravo | 2014 | 1 | 6 | Reality |
| Online Nation | The CW | 2007 | 1 | 4 | — |
| Only in America with Larry the Cable Guy | History | 2011–2013 | 3 | 50 | Reality |
| Only Murders in the Building | Hulu | 2021–on air | 5 | 50 | Mystery |
| OnTen | Voice of America | 2012 | 2 | 52 | — |
| Onyx EquinoxAnimated web series | Crunchyroll | 2020 | — | — | Science fantasy |
| Oobi | Nickelodeon | 2000–2005 | 3 | 52 | Puppetry |
| Ooh, Aah & You | Playhouse Disney | 2005–2011 | 2 | 40 | — |
| Open All Night | ABC | 1981–1982 | 1 | 12 | Sitcom |
| Open House | Fox | 1989–1990 | 1 | 24 | Sitcom |
| The Open Mind | | 1956 | — | 504 | Interview |
| Open Season: Call of NatureAnimated series | Family Channel | 2023–2024 | — | — | — |
| Opening Act | E! | 2012 | 1 | 8 | Reality |
| Operación pacífico | Telemundo | 2020–on air | — | 44 | Telenovela |
| Operation Alphabet | WPVI-TV | 1961–1965 | 2 | 190 | — |
| Operation: Entertainment | ABC | 1968–1969 | 1 | 31 | — |
| Operation Information | DuMont | 1952 | 1 | 10 | — |
| Operation Junkyard | NBC | 2002 | — | — | Action |
| Operation Petticoat | ABC | 1977–1979 | 2 | — | Comedy |
| Operation Repo | Telemundo | 2006–2014 | 11 | 286 | Pseudo-documentary |
| Opportunity Knocks | ABC | 2008 | 1 | 3 | — |
| Opposite Sex | Fox | 2000 | 1 | 8 | Comedy-drama |
| Opposite Worlds | Syfy | 2014 | 1 | 12 | Reality |
| The Opposition with Jordan Klepper | Comedy Central | 2017–2018 | 1 | 128 | — |
| Oprah's Big Give | ABC | 2008 | 1 | 8 | Reality |
| Oprah's Lifeclass | OWN | 2011–2014 | 5 | 63 | — |
| Oprah's Master Class | OWN | 2011–2018 | 5 | 43 | — |
| Oprah's Next Chapter | OWN | 2012–2015 | 3 | 85 | Talk show |
| Oprah: Where Are They Now? | OWN | 2012–2017 | 7 | 86 | Reality |
| The Oprah Winfrey Show | CBS | 1986–2011 | 25 | 4,561 | Talk show |
| Orange Is the New BlackWeb series | Netflix | 2013–2019 | 7 | 91 | Crime |
| Orangutan Island | Animal Planet | 2007–2009 | 2 | 26 | Documentary |
| The Order | Netflix | 2019–2020 | 2 | 20 | Fantasy |
| Ordinary Joe | NBC | 2021–2022 | 1 | 9 | — |
| The Oregon Trail | NBC | 1977 | 1 | 14 | Western |
| Origin | YouTube, YouTube Premium | 2018 | 1 | 11 | Speculative fiction |
| The Originals | The CW | 2013–2018 | 5 | 92 | Werewolf |
| Orleans | CBS | 1997 | 1 | 8 | Drama |
| The Orville | Hulu, Fox | 2017 | 3 | 36 | Science fiction |
| The Osbournes | MTV | 2002–2005 | 4 | 52 | Docu-soap |
| Osbournes Reloaded | Fox | 2009 | 1 | — | — |
| The OsmondsAnimated series | ABC | 1972 | — | 17 | Children's |
| OswaldAnimated series | Nick Jr. Channel, Nickelodeon | 2001–2003 | 1 | 26 | Children's |
| The Other Black Girl | Hulu | 2023–on air | 1 | 10 | Mystery |
| Other Space | Yahoo! Screen | 2015 | 1 | 8 | Science fiction |
| The Other Two | Comedy Central, Cinemax | 2019–on air | 3 | 30 | LGBTQ |
| The Others | NBC | 2000 | 1 | 13 | Science fiction |
| The Othersiders | Cartoon Network | 2007–2009 | 2 | 23 | — |
| Otherworld | CBS | 1985 | 1 | 8 | Science fiction |
| Our America with Lisa Ling | OWN | 2011–2014 | 5 | 44 | Documentary |
| Our BoysMiniseries | HBO | 2019 | 1 | 10 | Historical drama |
| Our Cartoon PresidentAnimated series | Showtime | 2018–2020 | 3 | 36 | Satire |
| Our Family Honor | ABC | 1985–1986 | 1 | 13 | — |
| Our Flag Means Death | HBO Max | 2022–2023 | 2 | 18 | Adventure |
| Our Generation | NBC | 2002–2005 | 3 | 61 | Drama |
| Our Great National Parks | Netflix | 2022–on air | 1 | 5 | Nature documentary |
| Our House | NBC | 1986–1988 | 2 | 46 | Sitcom |
| Our Kind of People | Fox | 2021–2022 | 1 | 12 | — |
| Our Little Family | TLC | 2015 | 2 | 17 | Reality |
| Our Man Higgins | ABC | 1962 | 1 | 34 | Sitcom |
| Our Place | CBS | 1967 | 1 | 10 | Musical |
| Our Private World | CBS | 1965 | 1 | 38 | Soap opera |
| Our Secret Weapon: The Truth | DuMont | 1950–1951 | — | — | — |
| Our WorldNews program | ABC | 1986–1987 | 1 | 26 | Documentary |
| Out All Night | NBC | 1992–1993 | 1 | 19 | Sitcom |
| Out of Control | Nickelodeon | 1984–1985 | 1 | 26 | — |
| Out of Jimmy's Head | Adult Swim | 2007 | 1 | 20 | Comedy |
| Out of OrderMiniseries | Showtime | 2003 | 1 | 6 | Comedy-drama |
| Out of Practice | CBS | 2005–2006 | 1 | 22 | LGBTQ |
| Out of the Blue | ABC | 1979 | 1 | 12 | Sitcom |
| Out of the Blue | Syndication | 1995–1996 | 1 | 22 | Sitcom |
| Out of the Box | Playhouse Disney | 1998–2004 | 3 | 82 | — |
| Out of This World | Syndication | 1987–1991 | 4 | 96 | Fantasy |
| Out There | Noggin | 2003–2004 | 2 | 26 | Drama |
| Out ThereAnimated series | IFC | 2013 | 1 | 10 | Comedy-drama |
| Outcast | Cinemax, Star Premium | 2016–2018 | 2 | 20 | Horror |
| The Outcasts | ABC | 1968–1969 | 1 | 26 | Western |
| OutDaughtered | TLC | 2016 | 10 | 74 | — |
| Outer Banks | Netflix | 2020–2026 | 5 | 50 | Adventure |
| The Outer Limits | ABC | 1963–1965 | 2 | 49 | Mystery |
| The Outer Limits | Showtime, Super Channel | 1995–2002 | 7 | 154 | Mystery |
| Outer Range | Prime Video | 2022–2024 | 2 | 15 | Western |
| Outlander | Starz | 2014 | 8 | 101 | Fantasy |
| Outlander: Blood of my Blood | Starz | 2025–on air | 2 | 12 | Fantasy |
| Outlast | Netflix | 2023–on air | 1 | 8 | Reality competition |
| Outlaw | NBC | 2010 | 1 | 8 | — |
| Outlaw Empires | Discovery Channel | 2012 | 1 | 6 | Documentary |
| Outlaws | NBC | 1960–1962 | 2 | 50 | Western |
| Outlaws | CBS | 1986–1987 | 1 | 12 | Science fiction |
| Outmatched | Fox | 2020 | — | 10 | Sitcom |
| Outnumbered | Fox News | 2014 | 10 | — | Talk show |
| The Outpost | The CW | 2018–2021 | 4 | 49 | Fantasy |
| The OutsWeb series | | 2012 | — | 13 | LGBTQ |
| The Outsider | NBC | 1968 | 1 | 26 | Detective |
| The OutsiderMiniseries | HBO | 2020 | — | 10 | Thriller |
| The Outsiders | Fox | 1990 | 1 | 13 | Drama |
| Outsiders | WGN America | 2016–2017 | 2 | 26 | Drama |
| Outsiders Inn | CMT | 2008 | 1 | 8 | Reality |
| OutsmartedWeb series | BuzzFeed | 2017 | 1 | 10 | Comedy |
| Outsourced | NBC | 2010–2011 | 1 | 22 | Sitcom |
| The Oval | BET | 2019–on air | 5 | 113 | Soap opera |
| Over My Dead Body | CBS | 1990–1991 | 1 | 11 | Police drama |
| Over the Garden WallMiniseries | Cartoon Network | 2014–2019 | 1 | 10 | Mystery |
| Over the Top | ABC | 1997 | 1 | 12 | Sitcom |
| Over There | FX | 2005–2006 | 1 | 13 | Drama |
| Over Your Head | HGTV | 2006 | 9 | 105 | Reality |
| Overcompensating | Prime Video | 2025–on air | 1 | 8 | College life |
| Overhaulin' | TLC | 2004–2015 | 8 | 107 | Reality |
| Overland Trail | NBC | 1960 | 1 | 17 | Western |
| Owen Marshall: Counselor at Law | ABC | 1971–1974 | 3 | 70 | — |
| The Owl HouseAnimated series | Disney XD, Disney Channel | 2020–2023 | 3 | 43 | Drama |
| Owner's Manual | AMC | 2013 | 1 | 8 | Reality |
| Oz | HBO | 1997–2003 | 6 | 56 | Crime |
| The Oz KidsAnimated series | ABC Kids | 1996 | 1 | 26 | Comedy-drama |
| Ozark | Netflix | 2017–2022 | 4 | 44 | Drama |
| Ozark Jubilee | ABC | 1955–1960 | 6 | 297 | Music |
| Ozark Law | A&E | 2025–on air | 1 | 2 | Reality |
| Ozzie's Girls | Syndication | 1972–1974 | 1 | 24 | Sitcom |
| Ozzy & DrixAnimated series | The WB | 2002–2004 | 2 | 26 | Fantasy |
| Ozzy & Jack's World Detour | History | 2016–2018 | 1 | 6 | Reality |