An offshore patrol boat or offshore patrol vessel (OPV) is a type of naval or coast guard ship specifically designed to conduct maritime security, surveillance, and law-enforcement operations in coastal and offshore waters, including exclusive economic zones (EEZs). These vessels are typically equipped with navigation radar, communication systems, light to medium weaponry, and sometimes small boats or helicopters, enabling them to perform missions such as border protection, anti-smuggling operations, anti-piracy patrols, search and rescue, fisheries enforcement, and environmental monitoring. Compared with larger warships, offshore patrol vessels are generally smaller, more fuel-efficient, and optimized for long-endurance patrols rather than heavy combat, allowing them to remain at sea for extended periods while maintaining operational readiness.

Offshore patrol vessels play a crucial role in maritime governance and national security, especially for countries with vast coastlines or significant offshore resources like oil, gas, and fisheries. Their versatility allows them to operate in various sea conditions, support humanitarian missions, and cooperate with international maritime agencies during joint operations or disaster response. Modern OPVs increasingly incorporate advanced surveillance technology, modular mission systems, and improved crew accommodations, reflecting the growing importance of persistent maritime presence and rapid response capability in safeguarding territorial waters and maintaining stability in regional seas.