Yokosuka is a city located in Kanagawa Prefecture, Japan, occupying most of the Miura Peninsula. It sits between the mouth of Tokyo Bay to the east and Sagami Bay on the Pacific Ocean to the west. The city serves as an important coastal municipality within the Greater Tokyo Area, recognized as the eleventh-most populous city in that region and twelfth in the Kantō area.

The area has been inhabited since the Paleolithic period, with Kinugasa Castle established in 1063 by local warlord Muraoka Tamemichi. During the Edo period, it was a strategic tenryō territory controlled by the Tokugawa shogunate. In 1865, French engineer Léonce Verny oversaw the creation of the Yokosuka Naval Arsenal, Japan's first modern arsenal, which played a pivotal role in the nation's industrial modernization.

The city is defined by its naval heritage and industrial infrastructure. It is home to United States Fleet Activities Yokosuka, which has served as a home port since 1945. The landscape includes remnants of over 260 caves built during World War II for secrecy. The Oppama area hosts significant automotive facilities, while the city also features the Hashirimizu waterway and historic brick factories from the Meiji era.

Yokosuka is famous for its culinary traditions, particularly Kaigun (Navy) curry, celebrated annually with a festival drawing 50,000 attendees. The city is also known for Miura daikon radish. Visitors are drawn to its historical sites, including monuments to William Adams and the preserved naval base facilities. The area offers tourist information through official English pages and local associations, highlighting its unique blend of military history and cultural tourism.

As of February 2024, the city has a population of 373,797 across an area of 100.7 square kilometers. Its economy relies on military facilities and manufacturing, notably Nissan Motors' Oppama plant which assembles vehicles like the Leaf and Cube. Transportation access is provided by the JR East Yokosuka Line and Keikyu Main Line, connecting the city to Tokyo and Yokohama via stations such as Yokosuka-Chūō.