The chief medical officer is the assigned officer of a starship or starbase who is responsible for overseeing the health and medical fitness of the assigned crew and passengers. He or she is in charge of the ship's sickbay department (or station infirmary) and oversees all medical activity onboard. They also take lead in major research projects for the general benefit of Federation knowledge. (TOS: "The Immunity Syndrome," )(TNG: "Clues," ), (TNG: "Suspicions," ). The position is generally a senior staff position.

Among Starfleet, CMO is a frequently used abbreviation. Chief medical officers were also referred to as the "ship's surgeon" in the 23rd century.

In addition to the usual rank duties of the officer, the CMO also has the power to relieve an officer, including a superior one, of their duties if in the officer's professional judgement, he or she is medically unfit. Typically, the CMO is expected to have the support of a senior command officer and/or detailed medical documentation to justify this course of action. (TNG: "Lonely Among Us," VOY: "Year of Hell, Part II")

Chief medical officers have been seen with a variety of ranks. They can hold any rank in the lieutenant grades, but are quite often seen as lieutenant commanders. Chief medical officers are eligible to take the Bridge Officer's Test for promotion to full commander. At this point, they are considered capable of assuming command of a starship. (TNG: "Thine Own Self")

List of chief medical officers



Alternate timelines and parallel universes



Decipher's Customizable Card Game states that the ill-fated lieutenant commander who was chief medical officer of the USS Voyager was named Fitzgerald. The novelization of Caretaker also listed him as Fitzgerald.
There have been several other chief medical officers of note in non-canon Star Trek stories, such as novels and comics:
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