Key Highlights
- The Indian Navy currently operates around 18 submarines, including two operational nuclear-powered ballistic missile submarines (SSBNs) in the Arihant class and approximately 16 diesel-electric attack submarines (SSKs) across Kalvari, Sindhughosh, and Shishumar classes.
- The fleet supports nuclear deterrence, anti-surface and anti-submarine warfare, intelligence gathering, and special operations, with a strong push toward indigenous design and construction.
- Evidence suggests the conventional submarines provide capable littoral operations, while the SSBNs strengthen India’s nuclear triad; however, the overall fleet size remains below the often-cited ideal of 24–30 boats for optimal coverage in the Indian Ocean Region.
- Ongoing upgrades (such as AIP retrofits) and major programs like Project 75I indicate steady progress toward a more modern and self-reliant underwater force.
Fleet Overview
India’s submarine arm forms a critical component of its maritime strategy, balancing legacy platforms from Russia and Germany with newer French-derived and indigenous designs. The two Arihant-class SSBNs deliver sea-based nuclear deterrence, while the six Kalvari-class (Scorpene) boats represent the most advanced conventional assets. Older Sindhughosh (Kilo) and Shishumar (Type 209) classes continue to serve but face age-related limitations. Submarines operate primarily from bases in Visakhapatnam on the east coast and Mumbai on the west coast.
Capabilities and Roles
Conventional submarines excel in stealthy patrols, torpedo and missile strikes, and mine-laying. The Kalvari class, for instance, can launch SM39 Exocet anti-ship missiles and heavyweight torpedoes. The Arihant class carries K-15 and K-4 submarine-launched ballistic missiles (SLBMs) for strategic deterrence. Public sources indicate the fleet contributes to anti-access/area-denial (A2/AD) strategies and supports broader naval operations in the Indian Ocean. AIP upgrades on Kalvari boats are expected to extend submerged endurance significantly.
Future Developments
Ambitious plans include six advanced SSKs under Project 75I (likely featuring German Type 214 technology with fuel-cell AIP) and indigenous nuclear-powered attack submarines (SSNs) under Project 77. Larger S5-class SSBNs are also in development. These initiatives aim to expand the fleet and enhance technological self-reliance amid regional security dynamics.
The Indian Navy’s submarine fleet represents one of the most strategically vital elements of India’s maritime power projection. From its early reliance on foreign designs to today’s growing emphasis on indigenous construction, the journey reflects both historical constraints and ambitious modernization goals. As of early 2026, the Navy operates a mixed fleet of approximately 18 submarines—two nuclear-powered ballistic missile submarines (SSBNs) and around 16 diesel-electric attack submarines (SSKs). This force supports a wide array of missions, including strategic deterrence, sea control, intelligence collection, special forces insertion, and anti-submarine warfare, all within the vast expanse of the Indian Ocean Region (IOR).
Historical Evolution
India’s submarine program traces its roots to the 1960s when the Navy acquired Soviet Foxtrot-class boats, marking the beginning of underwater operations. The 1980s saw the induction of German Type 209 submarines (Shishumar class) built under license at Mazagon Dock Limited (MDL), followed by Russian Kilo-class vessels (Sindhughosh class) in the late 1980s and 1990s. A significant milestone came with the Advanced Technology Vessel (ATV) program, which led to the indigenous Arihant-class SSBNs, leveraging substantial domestic research and some international collaboration, particularly on propulsion systems. The 2005 Project 75 contract with France’s Naval Group for Scorpene-derived submarines (Kalvari class) further advanced local build capabilities at MDL. Over decades, challenges such as delays, technology absorption, and the need for sustained industrial investment have shaped a more self-reliant but still evolving submarine industrial base.
Current Fleet Composition and Key Classes
Arihant-Class SSBNs (Nuclear-Powered Ballistic Missile Submarines)
These represent the sea leg of India’s nuclear triad. The class features a pressurized water reactor and can carry K-15 (750–1,500 km range) or longer-range K-4 (3,500 km) SLBMs.
- INS Arihant (S2): Commissioned 2016, approximately 6,000 tonnes displacement, active on deterrence patrols.
- INS Arighaat (S3): Commissioned August 2024, also on operational patrols.
- INS Aridhaman (S4) and a fourth boat: In advanced trials or nearing completion, with stretched designs offering greater missile capacity (up to 24 K-15 or 8 K-4 tubes) and displacements around 7,000 tonnes.
These boats, built at Visakhapatnam’s Ship Building Centre, underscore India’s ability to design and construct nuclear submarines indigenously, though noise levels and reactor maturity remain areas of ongoing refinement according to open analyses.
Kalvari-Class (Project 75 Scorpene) Diesel-Electric Attack Submarines
Six boats completed and commissioned by January 2025, making this the most modern conventional component of the fleet. These French-designed, Indian-built submarines displace about 1,775 tonnes submerged, reach speeds of 20 knots underwater, and feature six 533 mm torpedo tubes capable of firing torpedoes, Exocet anti-ship missiles, and mines.
| Submarine Name | Pennant | Commissioned | Status/Notes |
|---|---|---|---|
| INS Kalvari | S21 | Dec 2017 | Under refit; first AIP retrofit planned |
| INS Khanderi | S22 | Sep 2019 | Active |
| INS Karanj | S23 | Mar 2021 | Active |
| INS Vela | S24 | Nov 2021 | Active |
| INS Vagir | S25 | Jan 2023 | Active |
| INS Vagsheer | S26 | Jan 2025 | Active; last of the class |
A major upgrade program involves retrofitting DRDO-developed phosphoric acid fuel cell (PAFC) Air Independent Propulsion (AIP) systems. This technology promises to extend submerged endurance from days to 2–3 weeks by generating power without surfacing to snort. Contracts for AIP plugs and heavyweight torpedoes (including indigenous EHWT Takshak and Black Shark) were signed in late 2024, with integration beginning progressively. These enhancements will markedly improve stealth and operational flexibility in contested waters.
Sindhughosh-Class (Kilo) and Shishumar-Class (Type 209)
These older platforms—roughly six Sindhughosh and four Shishumar boats—provide essential numbers but are increasingly challenged by maintenance demands and technological obsolescence. Many have undergone mid-life upgrades, including new sonars and weapons, yet their diesel-electric nature limits prolonged submerged operations compared to AIP-equipped or nuclear vessels. Several older Kilos have been decommissioned in recent years, with the remaining units focused on training and secondary roles.
Table: Major Submarine Classes in Indian Navy Service (Approximate 2026)
| Class | Type | Active Boats | Displacement (submerged) | Origin/Notes | Primary Armament |
|---|---|---|---|---|---|
| Arihant | SSBN | 2 (more in trials) | ~6,000–7,000 t | Indigenous nuclear | K-15/K-4 SLBMs, torpedoes |
| Kalvari (Scorpene) | SSK | 6 | ~1,775 t | French design, Indian build | Torpedoes, Exocet missiles, mines |
| Sindhughosh (Kilo) | SSK | ~6 | ~3,000 t | Russian | Klub missiles, torpedoes |
| Shishumar (Type 209) | SSK | 4 | ~1,850 t | German design, Indian build | Torpedoes |
Operational Aspects and Strategic Role
Indian submarines train extensively in the Bay of Bengal and Arabian Sea, participating in exercises like TROPEX and international drills. The fleet’s bases allow coverage of both eastern and western approaches to the subcontinent. In strategic terms, the submarines contribute to deterrence against potential adversaries, particularly in the context of growing naval activities by China in the IOR and Pakistan’s expanding submarine fleet. The SSBNs ensure a survivable second-strike capability, aligning with India’s no-first-use nuclear doctrine. Conventional boats focus on sea denial, protecting sea lines of communication, and supporting carrier battle groups.
Future Plans and Expansion
India’s 30-year submarine-building perspective plan envisions a significantly larger and more advanced fleet. Key initiatives include:
- Project 75I: Six next-generation SSKs with advanced AIP, land-attack cruise missiles, and superior stealth. Negotiations with Germany’s ThyssenKrupp Marine Systems (TKMS) for Type 214-derived boats are advanced, with construction expected at MDL under strategic partnership models. This program emphasizes technology transfer and private sector involvement.
- S5-Class SSBNs: Larger follow-ons to Arihant (around 13,500 tonnes) capable of carrying more advanced SLBMs, including potential K-5/K-6 missiles with greater range and MIRV options. Construction of the first units has reportedly begun.
- Project 77 (SSNs): Up to six nuclear-powered attack submarines for high-speed, long-endurance operations. The first is targeted for the mid-2030s.
- Additional efforts: Integration of land-attack cruise missiles on conventional boats, submarine rescue capabilities, and unmanned underwater vehicles.
By the mid-2030s to 2040, projections suggest India could field 8–10 nuclear-powered submarines alongside a robust conventional force, potentially ranking among the world’s top nuclear submarine operators. The Navy aims for over 200 total warships and submarines by 2035, with indigenous content rising steadily.
Challenges and Achievements
Despite progress, the fleet faces hurdles: the current number of boats is modest relative to operational requirements and regional peers; older platforms strain logistics; and complex technologies like nuclear propulsion and AIP demand sustained expertise. Delays in programs like Project 75I highlight bureaucratic and industrial bottlenecks. On the positive side, the successful completion of all six Kalvari boats, operational patrols by Arihant-class vessels, and AIP development demonstrate growing mastery of submarine technology. Larsen & Toubro, Mazagon Dock, and DRDO have become key pillars of this ecosystem.
In summary, India’s submarine force is transitioning from a legacy-dependent navy to a modern, largely indigenous underwater arm. While gaps remain, the combination of strategic SSBNs, modernized SSKs, and ambitious future programs positions the Indian Navy to safeguard national interests effectively in an increasingly contested maritime domain. Continued investment in human capital, supply chain resilience, and international partnerships (where aligned with self-reliance goals) will determine the pace and success of this transformation.
