Massive amounts of conjecture is on this page to list in-universe Doppelgängers who have never been stated to be in-text. As per T:VALID, we cannot say something if the source doesn't tell us, and the mere reuse of actors is not good enough due to it being an occasional decision by movies and television to act as if two characters portrayed by the same actor do not look alike within a production.
These problems might be so great that the article's factual accuracy has been compromised. Talk about it here or check the revision history or Manual of Style for more information.
Doppelgängers were individuals who were identical to other individuals. According to the Second Doctor, the idea of a doppelgänger could be found in folklore and myth across almost every civilisation. It was suggested that if two doppelgängers met, one of them would die. (AUDIO: The Night Witches)
Known doppelgängers
Coincidental doppelgängers
Ian Chesterton and Robin Hood happened to look alike, (PROSE: The Thief of Sherwood) as did Polly Wright and Maid Marian, (PROSE: The Thief of Sherwood, That Time I Nearly Destroyed the World Whilst Looking for a Dress) and Tatiana Kregki, (AUDIO: The Night Witches) Strella and Romana I, (TV: The Androids of Tara) Ann Talbot and Nyssa, (TV: Black Orchid) Peri and Queen Anne (although Queen Anne had a crooked nose), (AUDIO: The Church and the Crown) William Pike and his great-grandson Darius Pike, (TV: The Cambridge Spy) Barker and his great-grandson Thorne, (TV: The Cambridge Spy) Gwyneth and Gwen Cooper, potentially due to spatial genetic multiplicity, (TV: Journey's End) cousins Adeola Oshodi and Martha Jones, (TV: Smith and Jones) and a Soothsayer and Amy Pond, (TV: The Fires of Pompeii)
The Doctor's doppelgängers
The Doctor had various doppelgängers across their regenerations. The First Doctor resembled the Abbot of Amboise (TV: The Massacre) and Solomon the trader. (TV: Dinosaurs on a Spaceship, Twice Upon a Time) Cardinal Robert Bellarmine also closely resembled him to the point of being mistaken for him by those unfamiliar with the Doctor. (PROSE: The Empire of Glass)
He also resembled Ramón Salamander in his second incarnation, (TV: The Enemy of the World) Premier Lutz in his third, (PROSE: Talons of Terror) Father Gregory in his fourth , (AUDIO: Tsar Wars) Andrew Edwardson in his fifth (AUDIO: My Dinner with Andrew) Commander Maxil in his sixth, (TV: Arc of Infinity, The Twin Dilemma) Edward Marlow in his eighth, (AUDIO: Other Lives) and Lobus Caecilius (TV: The Fires of Pompeii, The Girl Who Died) and John Frobisher in his twelfth. (TV: Children of Earth)
Deliberate doppelgängers
The Daleks created a robot double of the First Doctor, (TV: The Chase) the Chameleons adopted the appearance of several people including Polly, (TV:The Faceless Ones) General Scobie came face-to-face with his Auton replacement, (TV: Spearhead from Space) Bill Filer was duplicated by Axos, (TV: The Claws of Axos) the Zygons impersonated several people including Harry Sullivan, (TV: Terror of the Zygons) the Fourth Doctor, Sarah Jane Smith, Sergeant Benton, and Harry Sullivan were all duplicated as robots by the Kraals, (TV: The Android Invasion) Prince Reynart's robot double was crowned king in his place, (TV: The Androids of Tara) Cessair of Diplos created an image of the Doctor that caused Romana to fall over the edge of a cliff, (TV: The Stones of Blood) Romana II chose to take on the appearance of Astra of Atrios when she regenerated, (TV: The Armageddon Factor and Destiny of the Daleks) Meglos and the Fourth Doctor, (TV: Meglos) Omega and the Fifth Doctor, (TV: Arc of Infinity) Kamelion took on the form of King John of England and momentarily, the Fifth Doctor, the Tremas Master and Tegan Jovanka, (TV: The King's Demons) the Daleks created multiple duplicates, Stien amongst them, (TV: Resurrection of the Daleks) Sharaz Jek created android doubles of Major Salateen, the Doctor and Peri, (TV: The Caves of Androzani) a Kymbra Chimera took on the form of the Sixth Doctor and Peri Brown while in the Doctor's TARDIS, (COMIC: Changes) Dr. Who and the Seventh Doctor, (PROSE: Conundrum, Head Games) a clone of the Sixth Doctor, (AUDIO: Project: Lazarus) the Autons created a duplicate of Mickey Smith, (TV: Rose) Martha Jones was cloned by the Sontarans, (TV: The Sontaran Stratagem) Drake created a duplicate of K9, (TV: Jaws of Orthrus) the Autons created a duplicate of Rory Williams, (TV: The Pandorica Opens/The Big Bang) the Flesh was used to create "Gangers" of both the Eleventh Doctor and Amy Pond, among other characters, (TV: The Rebel Flesh/The Almost People and A Good Man Goes to War) the Justice Department Vehicle known as the Teselecta took the form of Grigori Rasputin with green skin, a caretaker, Erich Zimmerman, a Nazi soldier (both with and without a motorbike), Amy Pond, River Song, (TV: Let's Kill Hitler) and the Eleventh Doctor, (TV: The Wedding of River Song) the spirits of the 49th century took bodies on purpose so that they could be free once more (AUDIO: The Spirit Trap) and the Twelfth Doctor and Lobus Caecilius. (TV: The Girl Who Died)
Other
The Third Doctor travelled to a parallel universe and encountered other versions of Alistair Gordon Lethbridge-Stewart, Liz Shaw, and John Benton. (TV: Inferno) The Tenth Doctor travelled to a parallel universe and encountered other versions of Mickey Smith, Jackie Tyler, Pete Tyler, and the Cybermen. (TV: Rise of the Cybermen) Zagreus and the Eighth Doctor were identical. (AUDIO: Neverland, Zagreus) Townsend, Tepesh, and Winky were projections of the Seventh, Sixth and Fifth Doctors. (AUDIO: Zagreus) The Tenth Doctor transferred his regeneration energy to his hand, and when Donna Noble touched it, she created the Meta-Crisis Doctor. (TV: Journey's End)