The Virginia class (or SSN-774 class) is a class of nuclear-powered

Nuclear marine propulsion

Nuclear marine propulsion is propulsion of a ship by a nuclear reactor. Naval nuclear propulsion is propulsion that specifically refers to naval warships...

 fast attack submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s (SSN

Hull classification symbol

The United States Navy, United States Coast Guard, and United States National Oceanic and Atmospheric Administration use hull classification symbols to identify their ship types and each individual ship within each type...

) in service with the United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

. The submarines are designed for a broad spectrum of open-ocean

Blue-water navy

The term blue-water navy is a colloquialism used to describe a maritime force capable of operating across the deep waters of open oceans. While what actually constitutes such a force remains undefined, there is a requirement for the ability to exercise sea control at wide ranges...

 and littoral

Littoral

The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...

 missions. They were conceived as a less expensive alternative to the Seawolf class attack submarines

Seawolf class submarine

The Seawolf class is a class of nuclear-powered fast attack submarines in service with the United States Navy. The class was the intended successor to the , ordered at the end of the Cold War in 1989. At one time, an intended fleet of 29 submarines was to be built over a ten-year period, later...

, designed during the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

 era, and they are planned to replace the older of the Los Angeles-class submarines

Los Angeles class submarine

The Los Angeles class, sometimes called the LA class or the 688 class, is a class of nuclear-powered fast attack submarines that forms the backbone of the United States submarine fleet. With 43 submarines on active duty and 19 retired, the Los Angeles class is the most numerous nuclear powered...

, nineteen of which, from a total of 62 built, have already been decommissioned.
The Virginia class incorporates several innovations not previously incorporated into other submarine classes.
Instead of a traditional periscope

Periscope

A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....

, the class utilizes a pair of telescoping photonics mast

Photonics mast

A photonics mast is a sensor similar in concept to a submarine periscope, except that it doesn't require a periscope tube thus freeing design space duringconstruction and limiting risks of water leakage in the event of damage...

s located outside the pressure hull.