Series with the first letter - "T"
- The Octopus (1984)
- The Odd Couple (2015–2017)
- The Odd Couple (1970–1975)
- The Odyssey (1997)
- The Odyssey (1992–1994)
- The Offer (2022–…)
- The Office (2001–2003)
- The Office (2005–2013)
- The Office Blind Date (2022–…)
- The Old Man (2022–…)
- The One (2021–…)
- The Only Way Is Essex (2010–…)
- The Order (2019–…)
- The Original Ghostbusters (1986–1987)
- The Originals (2013–2018)
- The Orville (2017–…)
- The Osbournes Want to Believe (2020–…)
- The Other Two (2019–…)
- The Outer Limits (1963–1965)
- The Outer Limits (1995–2002)
- The Outlaws (2021–…)
- The Outpost (2018–…)
- The Outs (2012–…)
- The Outsider (2020–…)
- The Oval (2019–…)
- The Owl House (2020–…)
- The Pacific (2010)
- The Pacific War in Color (2018)
- The Pact (2015–…)
- The Pact (2021–…)