Doctor Who has the strongest record-backed claim to the longest-running science-fiction TV series, but “longest-running” can mean years on air, seasons, total episodes, or uninterrupted broadcasts. Those measures do not produce the same ranking. This list uses a dated editorial approach that combines revival seasons for returning series and ranks by seasons first, then episodes; it is not an official world-record ranking.
How this ranking works—and where it has limits
The ranking method matters because a programme with a long hiatus can span more calendar years than a series with more seasons or episodes. Specials, films, multipart stories, revivals and split episodes can also change totals depending on how they are counted.
- Metric: elapsed broadcast years, seasons, total episodes and consecutive broadcasts are different measures.
- Continuity: some series ran without interruption; others returned after a hiatus or as specials.
- Scope: a worldwide record is not interchangeable with a British or North American claim, and genre lists may treat animation differently.
A January 2026 editorial ranking offers one method: combine revival seasons for Doctor Who, The Twilight Zone and The X-Files where appropriate, then compare non-anime science-fiction series by seasons and total episodes. The evidence available for this article does not establish a consistent, current episode count for 13 candidates under one set of rules. Accordingly, the titles below are useful longevity comparisons, not a definitive ordinal list. For a genuine ranking, each candidate’s official episode guide would need to be checked using identical rules for specials and revivals.
What the best-documented examples show
Doctor Who: the clearest record-backed case
Guinness World Records describes the original BBC run of Doctor Who as 694 episodes across 26 seasons, broadcast from 23 November 1963 to 6 December 1989—26 years and 14 days. Guinness identifies that run as consecutive in its record description. Guinness World Records: longest-running sci-fi TV series.
#1 Best Overall
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- Sliders (Complete Series) - 4-Disc Boxset ( Sliders - Seasons One to Five )
- Sliders (Complete Series) - 4-Disc Boxset
- Sliders - Seasons One to Five
A separate Guinness record states that the programme aired its 819th episode on 29 April 2017. That milestone combined the original run with the series that returned in 2005, while excluding specials and the 1996 television movie. It is a dated record milestone, not a present-day episode count. Guinness World Records: episode-count record.
DoctorWho.tv announced a Christmas 2026 special, but that broadcast is in the future as of 7 October 2026 and should not be counted as an aired episode. DoctorWho.tv.
Stargate SG-1: a substantial North American run
Stargate SG-1 completed ten seasons and 214 episodes. That is a useful comparison for a long-running science-fiction series, but it is not the same category as Doctor Who’s worldwide Guinness record or its record for consecutive original-run episodes. Stargate SG-1 series record.
Red Dwarf: longevity across an original run and later returns
The official Red Dwarf site describes the BBC Two run from 1988 to 1999 as the second-longest-running British sci-fi series behind Doctor Who, while also documenting later specials and returns. The claim concerns British series longevity, not a shared episode-count ranking. Official Red Dwarf site.
Rank #3
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- Demon Slayer: Kimetsu No Yaiba - 4
- Demon Slayer: Kimetsu No Yaiba - 4
- Demon Slayer: Kimetsu No Yaiba - 4
- Demon Slayer: Kimetsu No Yaiba - 4
- Demon Slayer: Kimetsu No Yaiba - 4
Different lengths within one genre wave
A Television Academy retrospective counts Star Trek: Deep Space Nine at 173 episodes, Time Trax at 43 and Space Rangers at six. The contrast shows why “science-fiction series” alone does not imply comparable longevity. Television Academy retrospective.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why a definitive 13-place order needs consistent counting
An exact ranking can shift when the counting unit changes. A show with more seasons may have fewer episodes than another; a revival may be treated as a continuation or a separate series; and a special or television movie may or may not count toward a total. Even Guinness’s Doctor Who figures answer distinct questions: the 694-episode total covers the original consecutive run, while the 819th-episode milestone uses a wider, explicitly defined scope and a 2017 date.
Rank #4
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- 2-MOVIE COLLECTION – Includes two epic adaptations of Frank Herbert’s Dune saga.
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So a list labelled “ranked” should state its method and verify every entry from official episode guides before assigning all 13 ordinal positions. Without that reconciliation, a precise 1-to-13 episode order would imply a certainty the figures do not support. The defensible conclusion is narrower: Doctor Who leads the strongest documented longevity claim, while series such as Stargate SG-1, Red Dwarf and Star Trek: Deep Space Nine illustrate other forms and scales of long-running genre television.
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