For the use of the term in Star Trek see Chief Medical Officer (Star Trek).

The chief medical officer (CMO) is an official in the Republic of Ireland and United Kingdom who regularily advises their respective governments on health related matters. Such a person is the most senior advisor on health matters in both systems of government, and the term has also found some usage in non-government circles such as policing.

In any case of usage within these two countries the chief medical officer will be a qualified medical doctor whos duties will not include treatment but typically only advise such as public health matters. When appointed outside government the chief medical officer will often decide on physical and mental fitness to serve issues.

The equivalent United States term is Surgeon General, this term is also used with the British Armed Forces.