Sarah Jane Smith is a fictional character played by Elisabeth Sladen in the long-running BBC Television science fiction series Doctor Who and two of its spin-offs. Sarah Jane is a dogged investigative journalist who first encounters alien time traveller the Doctor while trying to break a story on a top secret research facility, and subsequently becomes his travelling companion on a series of adventures spanning the breadth of space and time. After travelling with The Doctor in four seasons of the show they suddenly part ways, and after this she continues to investigate strange goings-on back on Earth. Over time, Sarah Jane establishes herself as a committed defender of Earth from alien invasions and other threats, occasionally reuniting with The Doctor in the course of her own adventures, all the while continuing to work as a freelance investigative journalist.

Elisabeth Clara Heath-Sladen was an English actress. She became best known as Sarah Jane Smith in the British television series Doctor Who, appearing as a regular cast member from 1973 to 1976, alongside both Jon Pertwee and Tom Baker, and reprising the role many times in subsequent decades, both on Doctor Who and its spin-offs, K-9 and Company (1981) and The Sarah Jane Adventures (2007–2011).