Supplier · United Kingdom

MSubs

HQ Plymouth, United Kingdom

Plymouth-based UK builder of crewed and uncrewed underwater vehicles. It built XV Excalibur, the Royal Navy's Project Cetus extra-large uncrewed underwater vehicle (XLUUV), under a contract awarded in December 2022.

SupplierPrototypeNaval vessels and shipbuilding Uncrewed systems

Website

Systems

Most mature: prototype

Capabilities

Systems1

XV Excalibur

Royal Navy 12 m experimental extra-large uncrewed underwater vessel (XLUUV) built by MSubs under Project Cetus; in September 2026 it launched an exercise US Mk 48 heavyweight torpedo in an AUKUS trial.

Prototype

Newest unveiled first. Open a system for its milestone timeline, components and sources.

Capabilities2

Capabilities
Technology	Role	Maturity	TRL	Notes	Confidence
Naval vessels and shipbuilding	Supplier	—	—	classify_sectors run 37, haiku, taxonomy 2026-10-18b: Builds crewed and uncrewed underwater vehicles and built the Royal Navy's XV Excalibur XLUUV under a 2022 contract.	Reported
Uncrewed systems	Supplier	—	—	classify_sectors run 37, haiku, taxonomy 2026-10-18b: Builds crewed and uncrewed underwater vehicles and built the Royal Navy's XV Excalibur XLUUV under a 2022 contract.	Reported

Naval vessels and shipbuilding
Supplier
classify_sectors run 37, haiku, taxonomy 2026-10-18b: Builds crewed and uncrewed underwater vehicles and built the Royal Navy's XV Excalibur XLUUV under a 2022 contract.
—Reported
Uncrewed systems
Supplier
classify_sectors run 37, haiku, taxonomy 2026-10-18b: Builds crewed and uncrewed underwater vehicles and built the Royal Navy's XV Excalibur XLUUV under a 2022 contract.
—Reported

Maturity and TRL describe this organization's work; the field-wide maturity is on each technology's page.

Sources6

Profile3

1
NewsMSubs Launches First UK Navy XLAUV Drone Submarine in Plymouth
The Defense Post · Mar 7, 2025 · Supports Organization · description
“MSubs received the contract to build the first Cetus vessel in December 2022”
2
Regulatory filingM SUBS LIMITED
Companies House · Supports Organization · legal name
“M SUBS LIMITED Company number 05874602”
3
CompanyMSubs - Underwater vehicles and equipment
MSubs · Supports Organization · description, Organization · hq city
“Whether you’d like to discuss a manned or unmanned underwater vehicle, specialist engineering services, operational support or a potential partnership”

Systems3

4
Government recordHistoric first as Royal Navy launches torpedo from uncrewed submarine
Royal Navy · Sep 30, 2026 · Supports System
“XV Excalibur, an Extra-Large Uncrewed Underwater Vessel or XLUUV, was adapted with a specialist management system to successfully fire and control US Navy Mk48 Mod 4 Heavyweight Torpedo”
5
Government recordU.S. Navy and Royal Navy Successfully Test Fire Torpedo from Unmanned Undersea Vehicle
U.S. Navy · Sep 22, 2026 · Supports System
“from an allied uncrewed platform, the Royal Navy's XV EXCALIBUR”
6
Government recordRoyal Navy unveil 12 metre uncrewed submarine named after Excalibur
Royal Navy · May 15, 2025 · Supports Organization, System, System · maturity
“The crewless craft was built by Plymouth-based MSubs, who specialise in automated submersibles.”

Each fact on this page is attached to the sources that support it. Archived copies are linked when we keep one.