|Chief petty officer insignia|
|Starfleet, 2250s - 2260s|
|Starfleet, Mid 2370s|
|Starfleet, Late 2270s - 2350s|
|Starfleet, Late 2360s - Early 2370s|
Chief petty officer (CPO) is an enlisted naval rank, a type of military rank used by the service organizations of different cultures. As a traditional naval grade, CPO is senior to a petty officer, and is the highest enlisted grade in organizations like Starfleet and the US Navy. In comparison to infantry ranking systems, this rank is approximately equivalent to the more senior sergeant grades. Personnel of this grade can be addressed simply as chief, and sometimes by their job title, such as "chief specialist."
While chiefs are subordinate to all commissioned officers, they have far more experience and practical knowledge than ensigns and lieutenants, and are expected to act as mentors to them and to the junior enlisted assigned. As such, chiefs are often among the actual leaders in a Starfleet organization. Chiefs serve with distinction in most Starfleet branches and specialties, but are particularly visible in engineering and other technical trades.
There are usually individual grades of chief petty officers, differentiated by first, second class, etc; more senior CPOs are referred to as senior chief petty officer (SCPO) or master chief petty officer (MCPO), referred to as "senior chief" or "master chief" (respectively) in conversation.
When Sergey Rozhenko spied Miles O'Brien as the transporter chief aboard the USS Enterprise-D in 2367, Rozhenko was excited to meet another chief petty officer. When O'Brien introduced himself, he acknowledged Rozhenko as 'sir', to which Rozhenko told him not to call him 'sir', because he used to work for a living. Sergey's wife, Helena, then told O'Brien that he was just joking and that Sergey's proudest moment was when their son, Worf, had earned his commission. Sergey then added, "Imagine. An old enlisted man like me raising a boy to be an officer!" (TNG: "Family")
Several years later, O'Brien was identified by a Jem'Hadar as the rank of "Chief Petty Officer," or "what Starfleet refers to as a 'noncom'," adding "you must have a great deal of experience...that makes you a priority target." (DS9: "Hippocratic Oath")
List of chief petty officers
|Enlisted personnel||Commissioned officers||Generals and flag officers|
|ENS||LT JG||LT||LT CMDR||CMDR||CAPT||FCAPT||CDORE||RADM||VADM||ADM||FADM|
|2nd LT||1st LT||CAPT||MAJ||LT COL||COL||BRIG||MAJ GEN||LT GEN||GEN||MARSHAL|
|Positions:||Crewman • Technician • Chief||YMN||TAC • SO • 3rd • 2nd • 1st • CO • DD||Portmaster • Chief of Staff • CinC|
|Services:|| Andorian • Bajoran • Cardassian • Jem'Hadar • Klingon • Romulan • SS • Terran Empire Starfleet • Terran Empire MACO •|
United Earth MACO • United Earth/Federation Starfleet • United States • Vulcan
In Star Trek IV: The Voyage Home, a Chief Petty Officer contacts the CDO Commander Rogerson, regarding a power drain in the energy systems of the aircraft carrier Enterprise. The CPO's voice is not heard on screen, but the Commander responds to the question "Yes, Chief. We're tracking that too."