Clara Oswald is a companion to the Eleventh and Twelfth Doctors. According to the former, she was "not possible" due to their meetings previously in his personal timeline, with two such encounters seeing her die. Though assured by the empathic psychic Emma Grayling and the TARDIS scanner that Clara was just an "ordinary girl", the Doctor couldn't believe that to be true and thought her to be "the only mystery worth solving".
Amelia Jessica "Amy" Pond - sometimes styled Amelia Williams after her marriage - was the first companion of the Doctor in his eleventh incarnation. She was the girlfriend and later wife of nurse Rory Williams, and the mother of Melody Pond, who later became known as River Song. Amy died aged 87 at some point prior to 2012 after allowing a Weeping Angel to send her back in time, hoping to be reunited with her husband. She was buried beside Rory in a graveyard in New York.
Donna Noble, later Donna Temple-Noble, was a companion to the Tenth Doctor. Despite her humble beginnings, she was described by both Rose Tyler and the Tenth Doctor as being the most important woman in all of creation, due to the fact that she saved the whole of reality from the Daleks and Davros. To survive the side effects of her transformation into the "DoctorDonna", her memories of her time with the Doctor were forcibly erased and she was returned to Earth. She later married Shaun Temple, and became Donna Temple-Noble.
Dr. Martha Jones, later Martha Smith-Jones, was a British physician. She met the Tenth Doctor while in residency at Royal Hope Hospital in London when the hospital was transported to the Moon by the Judoon troops, after which she began travelling with the Time Lord. Unlike other companions, she not only became infatuated with the Doctor but also declared her feelings to him. She decided to stop travelling with him as he could not return her affection, but continued to have a number of adventures, both with and without him, thanks to her work with UNIT and Torchwood.
Trapped by Autons in the basement of Henrik's department store, shop assistant Rose Tyler’s life is saved by a chance encounter with the Doctor. When her heroism leads to the defeat of the Nestene, he invites her to travel with him – taking her from Victorian Cardiff to the day the Earth died. And although travelling with the Doctor was often dangerous, she told him she’d stay with him forever. Witnessing the Ninth Doctor’s regeneration only made that bond stronger. However, during the Battle of Canary Wharf they were separated – trapped on parallel worlds. Using a Dimension Cannon she attempted to make contact with the Doctor (and new companion Donna) several times, eventually encountering him as he was exterminated by a Dalek. Once healed and the Daleks defeated, he returned Rose to the parallel world with her family and the half-human version of himself, to live the rest of their lives together.