The Doctor (disambiguation)

"The Doctor" was the USS Voyager's Mark I Emergency Medical Hologram (EMH) who became the ship's chief medical officer.

Fan fiction
In Star Trek: Confederation the Doctor was copied, given a Confederation of Earth Science Division uniform, renamed as the Medical Doctor Hologram and was given the rank of Chief Medical Commander. His rank pips served as his mobile emitter. (Star Trek: Confederation: (Copied in) "Williams One" (Activated on the Reliant) "Deep Space Debacle")