Chief petty officer (CPO) is the seventh enlisted rank (with the paygrade E-7) in the United States Navy and U.S. Coast Guard, just above petty officer first class and below senior chief petty officer. The term "rating" is used to identify enlisted job specialties. In this way, enlisted personnel are segregated into three segments containing different enlisted ranks. Furthermore, rates are broken down into three levels: non-rated members without a designated occupation (E-1 through E-3). Advancement to E-4 and above is dependent on graduating from a specialty school that define what the enlisted is rated for. Petty officers (E-4 through E-6) and chief petty officers (E-7 through E-9) are part of the rated force and considered extremely knowledgeable about their particular rating. Examples include Culinary Services Chief and Aviation Maintenance Chief. The Chief Petty Officer is the rank

. Gunners Mate is a rating. E7 is a pay grade. The term rating is used to identify the career field of a chief petty officer. For example, the title of a chief petty officer in the Master-at-Arms rating would be spoken or spelled out as Master-at-Arms, Chief Petty Officer or Chief Master-at-Arms. The title would be abbreviated MAC. The grade of chief petty officer was established on 1 April 1893 in the United States Navy. The United States Congress first authorized the Coast Guard to use the promotion to Chief Petty Officer on 18 May 1920. Chief petty officer is also the final cadet grade in the United States Naval Sea Cadet Corps.

Prior to 1958, chief petty officer was the highest enlisted grade in both the U.S. Navy and U.S. Coast Guard. This changed with the passage of Pub.L. 85–422, the Military Pay Act of 1958, which established two new paygrades of E-8 and E-9 in all five branches of the U.S. Armed Forces. In the U.S. Navy and U.S. Coast Guard, the new E-8 paygrade was called senior chief petty officer (SCPO) and the new E-9 paygrade master chief petty officer (MCPO), with the first selectees promoting to their respective grades in 1959 and 1960.

Prior to establishment of the E-8 and E-9 grades, chief petty officers could typically serve in uniform for 30 or more years.

Shortly following establishment of the E-8 and E-9 grades, service limits currently known as high year of tenure (HYT) were established by pay grade. Although these limits periodically flex based on Fleet manpower requirements, current HYT limits restrict chief petty officers not selected for promotion to senior chief petty officer to 24 years of service, after which they face mandatory retirement.

Similar limits of 26 years for senior chief petty officer and 30 years for master chief petty officer are currently used, with a smaller core of master chief petty officers serving in command, force, and fleet master chief petty officer positions in the Navy, and area master chief or the Coast Guard Reserve Force Master Chief in the Coast Guard, being eligible to remain in uniform for 32 to 35 years and with the Master Chief Petty Officer of the Navy and the Master Chief Petty Officer of the Coast Guard being permitted to remain in uniform until reaching 38 years of service.