The Twin Dilemma is the seventh and final serial of the 21st season of the British science fiction television series Doctor Who, which was first broadcast in four twice-weekly parts from 22 to 30 March 1984.

The serial stars Colin Baker and Nicola Bryant as the Sixth Doctor and Peri Brown, respectively.

The serial follows the Doctor immediately after regenerating as he works to prevent the alien gastropod Mestor (Edwin Richfield) from plotting to explode the sun of the planet Jaconda to scatter his eggs throughout the universe to conquer it.

As a result of his recent regeneration, the Sixth Doctor suffers from mood swings and violent delusions, culminating in his attempt to strangle his companion, Peri Brown.

Realising the threat he could pose to the universe in this state, the Doctor decides to exile himself and Peri to a remote asteroid Titan 3.

The Doctor, Peri, and Hugo follow Azmael to the now-desolate Jaconda, where Azmael makes it clear he never intended for them to be harmed, and reveals that Mestor is forcing him to have Romulus and Remus create calculations which will terraform two nearby planets that the Gastropods can settle on.

The Doctor, however, realizes that Mestor has lied to Azmael about the nature of his plan, and the calculations will actually cause Jaconda's sun to go supernova, allowing Gastropod eggs to infest the galaxy.

Hugo decides to stay on Jaconda and become its new ruler, while the Doctor agrees to return Romulus and Remus to their parents.

[5] Prior to being cast, various media outlets had suggested Baker should be the one to replace Peter Davison as the next Doctor.

However, due to Baker's casting as Commander Maxil in Arc of Infinity he assumed he would be ineligible for the role.

[16] Peri's new outfit was originally a blue trouser suit, however Nathan-Turner opposed this as he felt she should wear something more revealing.

Baker suggested that in each subsequent story, the Doctor should wear a different cat badge to symbolise his mood.

[20] Where the previous serial, The Caves of Androzani, is frequently cast among the very best of all Doctor Who stories, The Twin Dilemma is often regarded as one of the very worst in the history of the series.

[5][21][23] Writing for Den of Geek, Andrew Blair felt that the quality of the serial partially devalued the ending of The Caves of Androzani.

The review also argues the script "leaves much to be desired" and that the direction is uninteresting, giving the whole story "a rather tacky, B-movie feel to it".

[25] In the 150th issue of SFX magazine Russell T Davies, producer of the 2005 revival, cites the story as "the beginning of the end" of Doctor Who.

The pair wrote, "How could anyone have thought that this story, of juvenile space monsters, meaningless plans and never-ending cop-outs, was ever workable?".

[5] Digital Spy's Morgan Jeffery also criticized the direction calling it "unusually flat" for Moffat.

[20] A novelisation of this serial, written by Saward, was published in hardback by Target Books in September 1985, and in paperback in March 1986.