The Doctor is a renegade Time Lord from the planet Gallifrey and the namesake of Doctor Who Earth. He regularly travels through time and space, usually with companions from Earth, aboard his TARDIS. His true name is unknown, having been erased after he left his home world to go on adventures. After the Last Great Time War, he is one of the last of the Gallifreyans. During his adventures, he regularly fights harmful beings such as the Daleks and the Cybermen. On occasion, he is recruited by the Elder Council to deal with threats to the universe.
Beginning with his first incarnation, the Doctor has developed a strong passion for the planet Earth and its people, largely because of their potential and diversity. During his third incarnation, he even chose it as his primary place of residence and bought property in Kent. He has also developed a close relationship with the United Nations organization UNIT, which has many times called upon his help.
On occasion, he has been known to visit Megacrossover Earth, although this has become rare in more recent times as his home universe was shielded from the rest of the multiverse following the Great Time War.
One of the great mysteries of the multiverse is the Doctor's true name. When he originally left Gallifrey, his name was removed from all records by the Time Lords, as was customary for their race. Although the Doctor remembers his original name, he prefers to keep it a secret and has only revealed it to a few individuals, including his companion Samantha Jones and his wife River Song. On Earth, he has been known to use the alias "John Smith" and variations thereof.
The Doctor was born from the Loom of the House of Lungbarrow. The details of his parents are unknown, although some claim that his mother was a human woman.
Throughout his long life, the Doctor has been married many times and has had children on several worlds, including Earth. Usually, these children are born to the same species as their mother with a small bit of Time Lord DNA. His children and grandchildren often shared a similar desire for adventure and helping others.