A few of the companions have died during the course of the series. Katarina sacrificed herself by opening her airlock to save the others from the mad fugitive Kirksen, and was blown into the vacuum of space. In the same serial, Sara Kingdom was rapidly aged to dust by a Time Destructor. While Adric attempted to divert a spaceship from crashing into Earth, a Cyberman destroyed the controls, they hurtled through time and crashed into the planet, creating the Chicxulub crater and causing the K-Pg extinction event (this fulfilled Silurians’ prophecy and facilitated the evolution of mammals).
The android Kamelion, after coming under The Master’s control, convinced The Doctor to destroy him, and the Doctor complied.
Astrid Peth sacrificed herself to kill Max Capricorn, saving the lives of millions aboard the interstellar space liner RMS Titanic and in the greater London area.
Before River Song’s formal companionship began, she sacrificed herself in order to save those trapped in the Library’s computer servers’ simulations. The Doctor uploaded her “data ghost” into the library servers, from which she later is able to communicate across time and space with Madame Vastra, Jenny Flint, Strax, and Clara Oswald in “The Name of the Doctor”. Adelaide Brooke killed herself after The Doctor altered the timeline by rescuing her, this ensured that her descendants will explore the galaxy and the wider universe as originally destined. Rory Williams is touched by a Weeping Angel in 2012 and sent back in time. With the encouragement of her daughter, River Song, and against The Doctor’s pleas, Amy Pond allows herself to be touched by a Weeping Angel in 2012 in the hope of being reunited with her husband in the past. She is successful, and they grow old together in New York City, die, and are buried in Queens on the spot from which they will later be sent back in time in 2012. In fighting the Ice Governess in the final hour of Christmas Eve 1892, a Victorian era incarnation of Clara Oswald falls off of the cloud on which the TARDIS was parked, plummeting to the ground. Another incarnation of Clara Oswald (named Oswin Oswald) dies in “Asylum of the Daleks”, the character disabling the planet’s shielding thus enabling The Doctor, Amy Pond and Rory Williams to escape.
Not all companion deaths have been permanent however. Jack Harkness resurrects after each death, having been made immortal by Rose Tyler in “The Parting of the Ways”. Rory Williams suffered several deaths, each of which was negated by alternate timelines, paradoxes, resurrection by advanced alien medicine, or the rebooting of the universe. Clara Oswald dies in “Face the Raven”, but in a subsequent episode (“Hell Bent”) her time stream is frozen at the moment of death by the Time Lords so that they can interrogate her about the Hybrid, The Doctor takes advantage of this to save her life, but she remains technically neither alive nor dead, does not age or have a pulse. After her departure as a companion of the Twelfth Doctor, she teams with the immortal Ashildr and travels in a stolen TARDIS.
Other companions died in alternate timelines or alternate lives. Brigade Leader Alistair Lethbridge-Stewart, Section Leader Liz Shaw, and Platoon Leader John Benton all died in the destruction of their universe’s Earth. Sarah Jane Smith, her son Luke Smith, Maria Jackson, &, Clyde Langer perished while trying to stop the Plasmavore and the Judoon in Royal Hope Hospital on the Moon in the parallel universe of “Turn Left”. In the same story, Martha Jones suffocated after giving up her oxygen to classmate/co-worker Oliver Morgenstern while on the Moon. Teenaged Sarah Jane Smith also died after falling from a pier in place of her friend, Andrea Yates, Maria Jackson convinces the adult Yates to correct the timeline, restoring Sarah Jane to life. After surviving decades in an alien hospice that was deadly to humans, Amy Pond compelled Rory Williams to lock her out of the TARDIS in order to protect her younger self and allow the latter to have the life with Rory that the former missed. Amy and Rory jointly jumped off of a high-rise in New York on a hunch that doing so would create a paradox and deliver themselves from that timeline.
Several other companions have died subsequent to their companionships. Sir Alistair Lethbridge-Stewart’s death months earlier was revealed in”The Wedding of River Song”, and he was later remembered fondly by his daughter and the Eleventh Doctor. Harry Sullivan’s death was implied by Sarah Jane Smith when he was the only former companion of whom she spoke in the past-tense and she remarked that she loved him. When the series was relaunched in 2005, The Doctor believed himself to be the only Time Lord to have survived the Last Great Time War, indicating that he believes that Susan Foreman and Romana were killed, and that Leela, who settled on Gallifrey,  was lost when that planet was destroyed in the Last Great Time War. However, the fiftieth anniversary episode”The Day of the Doctor ” reveals that the planet still exists in a separate pocket universe, leaving their fates uncertain. In 2050, Sarah Jane Smith is implied to be dead by Rani Chandra in “The Mad Woman in the Attic”. Vicki left the First Doctor circa 1250 BCE and passed into legend as Cressida.
LIST OF COMPANION DEATHS
During the course of the show’s history, there have been a few occasions when companions have died while on adventures with The Doctor. They are:
It should be noted that, of the examples given above, only Adric and Clara and were ongoing, “long-term” companions of the Doctor. All others listed either appeared for the first time and died in the same storyline (Sara, Astrid, Adelaide), or died in their second on-screen appearance in a Doctor Who storyline (Katarina, Kamelion, K9 Mark III).
Others are implied or stated to have died years after parting company with The Doctor.
The Eleventh Doctor learns of the death of the Brigadier Lethbridge-Stewart in”The Wedding of River Song” via phone call, coinciding with the death of the actor who portrayed him, Nicholas Courtney.
In “The Angels Take Manhattan “, Rory Williams and Amy Pond are displaced in time by a Weeping Angel, Amy allows the Angel to send her back so she can be with Rory. A gravestone reveals they died, Amy at the age of 87 and Rory age 82.
In The Trial of a Time Lord, Peri Brown is killed by King Yrcanos in Mindwarp, after her brain has been replaced by that of Kiv, a member of the Mentor race. However, in The Ultimate Foe it is revealed that Peri had not been killed and had instead become Yrcanos’ consort.
Grace Holloway is killed by The Master but revived by the TARDIS’ link to the Eye of Harmony during The TV Movie.
Jack Harkness is killed by Daleks but is brought back to life and given immortality by Rose Tyler in “The Parting of the Ways”. He has since died numerous times in both Doctor Who and Torchwood, always returning to life soon after. In “Last of the Time Lords”, it is implied that Harkness becomes the Face of Boe, who dies peacefully in “Gridlock” after living for billions of years.
River Song sacrifices herself in “Forest of the Dead” to save The Doctor’s life, but he is able to upload a digital copy of her consciousness to the data core. River continues to appear in the series at earlier points in her life, and her post-death consciousness reappears in”The Name of the Doctor “.
Sarah Jane Smith dies as a teenager in an alternate timeline in Whatever Happened to Sarah Jane?.
Rory is also killed by the Silurian Restac at the conclusion of “Cold Blood”, sacrificing himself to protect The Doctor. He is subsequently consumed by a crack in time, which wipes him from existence. He reappears in “The Pandorica Opens” as an Auton duplicate, created from Amy Pond’s memories, and is restored to his old life along with the rest of the universe in”The Big Bang”.
Rory is shown dying of old age in “The Angels Take Manhattan “, in front of himself, Amy, the Eleventh Doctor and his daughter River Song. He and Amy negate the timeline by jumping off a roof, thereby preventing him from being sent further back in time to die of old age downstairs. This kills both him and Amy, but both are resurrected as the timeline where they died is negated.
An older version of Amy Pond is killed by a handbot in “The Girl Who Waited” as it gives her medicine it doesn’t know will kill her, but her existence is erased when The Doctor and Rory are able to convince her to help them rescue the younger Amy, allowing them to erase the timeline where the older Amy existed.
The parallel world from” Turn Left” sees the off-screen deaths of the Sarah Jane Smith and Martha Jones of that world.
SPIN OFF MEDIA
A number of companions have died in spin off media as well as several spin off exclusives companions have died but this list is only concerned with companions:
Liz Shaw dies in the 1997 Virgin New Adventures novel Eternity Weeps by Jim Mortimore, the victim of an extraterrestrial terraforming virus contracted while part of a UNIT team investigating an alien artefact on the Moon. This is later contradicted by the Sarah Jane Adventures episode “Death of the Doctor ” which indicates that Liz Shaw is still alive – although still working on the moon – in 2010, the novel is set in 2003.
Ace is killed by an explosion in the comic storyline Ground Zero while still a companion of the Seventh Doctor. This is also contradicted by the Sarah Jane Adventures storyline”Death of the Doctor ” that indicates she is still alive in 2010, no longer travelling with The Doctor, and running a charity called ACE.
Jamie McCrimmon dies an elderly man in comic storyline The World Shapers.
Nyssa sacrifices herself so that her fellow companions can escape E-space in the Big Finish Productions audio The Entropy Plague.
Adam Mitchell is killed by an explosion in the comic storyline Prisoners of Time, sacrificing himself to thwart The Master’s attempt to destroy reality and saving all eleven Doctors and their gathered companions.