The INS Arihant (Sanskrit for 'Destroyer of Enemies') is the lead ship of India's class of indigenously built, nuclear-powered ballistic missile submarines (SSBN), designated S2 Strategic Strike Nuclear Submarine. It is a military vessel that serves as the sea-based leg of India's nuclear deterrent, completing the nation's nuclear triad (land, air, and sea).
The submarine's development began under the secretive Advanced Technology Vessel (ATV) project, which was sanctioned by Prime Minister Indira Gandhi in 1974 following the deployment of a US nuclear-powered carrier battle group during the 1971 Indo-Pakistani War. The project was re-aligned after the 1998 Pokhran-II nuclear tests to focus on a ballistic missile submarine, providing a survivable second-strike capability essential for India's 'No-First-Use' nuclear doctrine. Construction began in the early 2000s, and the 6,000-tonne vessel was launched on July 26, 2009, and commissioned into the Indian Navy in August 2016.
The INS Arihant is powered by an 83 MW Pressurized Water Reactor (PWR) using enriched uranium, which allows it to remain submerged for extended periods, limited only by crew provisions. Its primary mechanism is its armament of four vertical launch tubes, which can carry either twelve short-range K-15 Sagarika Submarine-Launched Ballistic Missiles (SLBMs) with a range of 750 km or four intermediate-range K-4 SLBMs with a range of 3,500 km. The submarine also has six 533 mm torpedo tubes.
The INS Arihant is the first of its class, which connects to its successors, the INS Arighaat (S3, commissioned in August 2024) and the larger INS Aridhaman (S4, commissioned in April 2026). While INS Arighaat maintains the same 6,000-tonne displacement and missile capacity as INS Arihant, the newer INS Aridhaman is a larger, 7,000-tonne "stretch" variant. This larger design allows INS Aridhaman to carry a doubled missile payload of up to eight K-4 or twenty-four K-15 missiles, marking a significant upgrade in the class's strategic capability.