The first person to have historically used anaesthesia to perform surgery was a dentist!
William Thomas Green Morton was the first dentist to use anaesthesia to achieve a painless tooth extraction on September 30th 1846. He used ether as an anaesthetic agent in his own dental office. Then, on October 16, 1846, Morton participated in a surgery where Dr. John Collins Warren used ether as anaesthesia on a patient at Massachusetts General Hospital to remove a tumour in the neck without pain. Following this procedure, the news spread out globally and Morton convinced the medical world of the importance of performing surgical procedures without pain.