Shonan (湘南) is the name of a resort-oriented region along the coast of Sagami Bay in central Japan. Centered around Enoshima, an island about 50 kilometers southwest of Tokyo, the Shonan region stretches from Oiso (大磯) in the west to Hayama (葉山) in the east, including Kamakura (鎌倉) and Hiratsuka (平塚). Because of the bay, the region benefits from a mild climate and long beaches covered with dark volcanic sand.

In postwar times, the Shonan region gained prominence in Ishihara Shintaro's prize-winning 1955 novel, Taiyo no Kisetsu (Season of the Sun). The novel portrayed the hedonistic lifestyle of young sun-worshippers from elite families (the "sun-tribe"), who hung out on Shonan beaches. Lying as it does on the edge of the Tokyo-Yokohama metropolitan area, the Shonan region is nowadays a leading resort area, oriented to surfing, sailboating, and other water sports.

The region's name, Shonan, derives from a scenic region in Hunan, China, encapsulated in the phrase 瀟湘湖南 (Chinese: xiao1 xiang1 hu2 nan2; Japanese: shosho konan). This phrase refers to a beautiful area centered around the Xiao River (瀟江) and the Xiang River (湘江) south of the Chang Jiang (長江: also called Yangzi or Yangtse River in English) in Hunan. Often praised in Chinese poetry, its scenery became a popular subject of paintings in both medieval China and Japan. In Japan, the scenery of the Shonan area was thought to be similar to the scenery around the Xiao and Xiang rivers in Hunan, China; hence the term "Shonan" (Chinese: "xiang1 nan2," another name for the Hunan region) came to be applied to the area around Enoshima in Japan.

Besides the similarity in scenery, the two areas both had flood-basin lakes. The lake in China, which still exists, is Lake Dongting (洞庭湖). Among others, the lake is fed by the Xiang and Xiao rivers (the Xiao is a tributary of the Xiang). In Japan, the corresponding flood-basin lake (which no longer exists but was mentioned in the Enoshima Engi) was probably located along the course of the Kashio River, which flows into Sagami Bay (via the Katase River) at Enoshima.