Which real-life surgeon did Conan Doyle say inspired his character Sherlock Holmes?

Joseph Bell FRCSE (1837-1911).

Dr. Bell was a surgeon who also lectured at the University of Edinburgh's medical school. He put particular emphasis on careful observation as part of the diagnostic process.

Some consider Bell to be a pioneer in forensic science.

He was Queen Victoria's personal surgeon on her visits to Scotland, and wrote medical textbooks.

Arthur Conan Doyle met him in 1877, working as Bell's clerk at the Edinburgh Royal infirmary. Doyle's "Sherlock Holmes" stories were loosely based on Dr. Bell, something the latter was aware of.

https://en.wikipedia.org/wiki/Joseph_Bell