An OPNAVINST or OPNAV Instruction is a formally documented lawful order that is issued by the Chief of Naval Operations

Chief of Naval Operations

The Chief of Naval Operations is a statutory office held by a four-star admiral in the United States Navy, and is the most senior uniformed officer assigned to serve in the Department of the Navy. The office is a military adviser and deputy to the Secretary of the Navy...

. These instructions are typically used to establish United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 policy, procedures, and requirements. The instructions are issued in the form of a memorandum

Memorandum

A memorandum is from the Latin verbal phrase memorandum est, the gerundive form of the verb memoro, "to mention, call to mind, recount, relate", which means "It must be remembered ..."...

 on official United States Navy letterhead

Letterhead

A letterhead is the heading at the top of a sheet of letter paper . That heading usually consists of a name and an address, and a logo or corporate design, and sometimes a background pattern...

. Each instruction is referenced with an OPNAVINST directive number and a date. Typically, when a new instruction supersedes a previous instruction, a cancellation notice citing the prior OPNAVINST number is included.