Doctor Who is a long-running British science fiction television series that has gained a large and devoted following around the world. The show centers around the Doctor, a time-traveling alien known as a Time Lord, and his companions as they travel through time and space in the TARDIS, a sentient time machine. The show has a rich and complex mythology, featuring iconic villains such as the Daleks and Cybermen, and has explored themes such as the nature of time and the human condition. Doctor Who has been praised for its imaginative storytelling, compelling characters, and its ability to reinvent itself over the years, making it a beloved staple of science fiction television.