Starfleet Security is the division of the Federation Starfleet tasked with maintaining security. It was headed by the Chief of Starfleet Security. Security officers aboard all Starfleet vessels and installations were considered members of Starfleet Security.

In some continuities, Starfleet Security is a distinct division from Starfleet Intelligence. In others, one division is subordinate to the other.

Rivalries and outright "turf wars" between Starfleet Intelligence and Starfleet Security often went on, unbeknownst to the general public and to most Starfleet personnel. Such a rivalry was known as a "Big Game". (Cloak and Dagger)

In the 2260s, Admiral Chen was a flag officer of the division. (Cloak and Dagger)