Katherine "Kathy" Chambers (born 1966) was the childhood best friend and high school classmate of Peri Brown and, as an adult, a friend and doctor to Tegan Jovanka. She was the daughter of Anthony Chambers and the younger sister of Nathaniel "Nate" Chambers. She grew up in Fell's Point, Baltimore, Maryland in the United States.
In September 1984, her father was seemingly killed by the Cyber-Leader, although the Baltimore Police were operating on the misapprehension that he had been murdered by a vagrant named Daniel Woods. By the time that Peri returned to Fell's Point to attend Anthony's funeral on 28 September 1984 with the Sixth Doctor, Kathy had not seen Peri for four months. However, several years had passed in Peri's personal timeline. In the meantime, Kathy's grades had improved enough to get into medical school. During the siege of Anthony's undertaking offices, she was appalled at cyber-converted Anthony's distress. His attack on her brother Nate paralysed him and made her despise the Doctor. (AUDIO: The Reaping)
While at university, she met James Clarke, who was interested in the cyber-conversion unit left by Peri at her home. Several months later, Kathy activated the device which had a self-destruct mechanism that activated in the event of tampering, killing Peri's mother Janine Foster and Dominique van Gysegham in the process. Kathy blamed herself for their deaths, which led her to move to Brisbane, Australia with James and her quadriplegic brother. (AUDIO: The Reaping, The Gathering)
In Brisbane, she founded Chambers' Pharmaceuticals, where she hoped to find cures for cancers and other diseases. When the Fifth Doctor arrived asking about alien technology on 22 September 2006, she took him to the bar 8687, where he was reunited with Tegan, who had previously been of his companions. She used the cyber-conversion technology to create a system to cure any disease. Tegan was to be its first patient. However, the Doctor persuaded the partially cyber-converted Nate to destroy it, which resulted in his own death. This was yet another death for which Kathy blamed herself. She was later arrested by the Brisbane Police. (AUDIO: The Gathering)