The Sixth Doctor Adventures is a Big Finish Productions audio play series based on the television series Doctor Who. It sees the return of Colin Baker reprising his role as the Sixth Doctor.

In 1999, beginning with the story The Sirens of Time, Big Finish Productions began producing a series of audio adventures featuring the Fifth Doctor, Sixth Doctor and Seventh Doctor. For 22 years these stories continued collectively known as Big Finish's Main Range.^[1][2] In May 2020, Big Finish announced the main range would conclude in March 2021 and subsequently replaced with regular releases of each Doctor's adventures continuing in their own respective ranges.^[3][4] Several previously released special titles were retroactively reallocated into these new ranges by Big Finish.

The Sixth Doctor: The Last Adventure is a British audio drama based on the series. Within the narrative of the series, the Doctor, its principal character, is a time-travelling alien known as a Time Lord, whose biological characteristics allow him to regenerate into a new form to circumvent an otherwise deadly experience; the device has been used to allow for a change in lead actor every few years in the production of the televised series.^[12] The sixth such instance was depicted in 1987 at the very beginning of Time and the Rani, but due to the firing between seasons of Sixth Doctor actor Colin Baker, the episode gave the event very little screen time and didn't explain what had caused it.

Big Finish Productions producer David Richardson approached Baker in 2014, after seeing "The Time of the Doctor", which had depicted (on television) the regeneration of the Eleventh Doctor into the Twelfth: "I felt very strongly that regeneration stories, and each Doctor’s final end, are very important to Doctor Who fans – these are stories that allow us to see the Doctor at his most courageous, making a sacrifice that only makes us love him more." Baker, who had been working with Big Finish since 1999, agreed to participate, saying that his depiction of the Doctor "did not benefit from" the difficult circumstances the show faced in the 1980s, and that the quality of Big Finish's work was "the only reason [he had] agreed to bring [his] Doctor to an end."^[13]

The audio drama consists of four one-hour episodes, each by a different author and each pairing the Doctor with a different companion and taking place at a different point in his life, but all unified by the presence of the villainous Valeyard, a potential future version of the Doctor introduced in Baker's last television serial, The Trial of a Time Lord. Besides Baker, Michael Jayston and Bonnie Langford reprised their roles from The Trial of a Time Lord, respectively as the Valeyard and as the Doctor's companion Mel.

The final part (The Brink of Death) explains that the Sixth Doctor dies due to the radiation of the planet Lakertya as part of his sacrifice in order to stop the Valeyard from taking over existence.

On 30 June 2023, two boxsets were scheduled for 2024.^[20] The first is scheduled for March 2024.^[21] Big Finish's Senior Producer John Ainsworth teased that it would follow "the Sixth Doctor celebrates his 40th anniversary by encountering some old acquaintances".^[20]

On 23 May 2024, Big Finish announced their slate of boxsets for 2025. Senior Producer John Ainsworth said “The Sixth, Seventh and Eighth Doctors will feature in two box sets each, as in previous years. I shan't give too much away but expect companions old and new, some classic series monsters that haven't featured on audio for a decade, and a name that's been hiding in plain sight (and it's time to go there...).”^[23] The first boxset is scheduled for May 2025.^[24]