Lady Isobel Barnett (June 30, 1918 - October 20, 1980) was a British radio and television personality, popular during the 1950s and 1960s.

Isobel Barnett was born in Aberdeen, Scotland. She was a practising doctor, and appeared as an actress, but it was as a panellist on BBC television shows such as What's My Line that she became famous. Elegant and witty, she was regarded by audiences as the epitome of the British aristocracy (although her title actually came from the fact that her solicitor husband had been knighted; she was not an aristocrat, nor had she married into the aristocracy). She also made regular appearances on the long-running (1948 to date) BBC Radio series "Any Questions?", on the radio panel game "Many A Slip" and on the now very dated women's discussion series "Petticoat Line".

When the more informal culture of the 1960s and 1970s brought an end to her television career, she descended into a reclusive and eccentric existence. In 1980, she was found guilty in court of a shoplifting offence, an event which briefly brought her back into the public eye. A few days later she was found dead in her home, having committed suicide. Her story was sensitively recounted by several of her friends and colleagues in a 1991 BBC Radio 4 documentary in the "Radio Lives" series, which confirmed that she gave no indication whatsoever to any of her friends that she was planning to take her own life, and that she kept up a facade of "business as usual".