Wokou (Chinese: 倭寇; pinyin: Wōkòu; Japanese: 倭寇; Hepburn: Wakō; Korean: 왜구; Hanja: 倭寇; RR: Waegu; literal Chinese translation: "dwarf bandits"), which translates to "Japanese pirates", were pirates who raided the coastlines of China and Korea from the 13th century to the 17th century. The wokou were made of various ethnicities of East Asian ancestry, which varied over time and raided the mainland from islands in the Sea of Japan and East China Sea.

Wokou activity in Korea declined after the Treaty of Gyehae in 1443 but continued in Ming China and peaked during the Jiajing wokou raids in the mid-16th century. Chinese reprisals and strong clamp-downs on pirates by Japanese authorities saw the wokou disappear by the 17th century.

There are two distinct eras of wokou piracy. The early wokou mostly set up camp on the outlying islands of the Japanese archipelago in the Sea of Japan, as opposed to the 16th-century wokou who were mostly non-Japanese. The early wokou raided the Japanese as well as the Chinese and Koreans.

The first recorded use of the term wokou (倭寇) is on the Gwanggaeto Stele, erected in modern Ji'an, Jilin, China to celebrate the exploits of Gwanggaeto the Great of Goguryeo (r. 391–413). The stele states that "wokou" ("Japanese robbers") crossed the sea and were defeated by him in 404. The term wokou is a combination of the Chinese terms Wō (倭), referring to either dwarfs or pejoratively to the Japanese, and kòu (寇) "bandit".

The origin of the term wokou dates back to the 4th century, but among wokou's activities, which are divided into two academic periods, the pirates called "early wokou" were borne from the Mongol invasions of Japan. As a result of the war, the coastal defense capabilities of China and Korea were significantly reduced, and the people living in Tsushima, Iki, and Gotō Islands in Kyushu suffered extreme poverty. For these reasons, wokou gradually intensified their looting on the coasts of China and Korea. Chŏng Mong-ju was dispatched to Japan to deal with the problem. During his visit, Kyushu governor Imagawa Sadayo suppressed the wokou, returning their captured property and people to Korea. In 1405, Ashikaga Yoshimitsu sent 20 captured pirates to China, where they were boiled in a cauldron in Ningbo.

According to Korean records, wokou were particularly rampant roughly from 1350. After almost annual invasions of the southern provinces of Jeolla and Gyeongsang, they migrated northwards to the Chungcheong and Gyeonggi areas. The History of Goryeo has a record of sea battles in 1380 whereby one hundred warships were sent to Jinpo to rout Japanese pirates there, releasing 334 captives. Wokou sorties decreased thereafter. The wokou were effectively expelled through the use of gunpowder technology, which the wokou lacked, after Goryeo founded the Office of Gunpowder Weapons in 1377 (which was abolished twelve years later).

In 1419, the Korean army landed in Tsushima and started the Ōei Invasion, the largest operation against the wokou. General Yi Chongmu's fleet of 227 ships and 17,285 soldiers set off from Geoje Island toward Tsushima on 19 June 1419. According to "Veritable Records of the Joseon Dynasty" a Korean history book, on 20 June the Korean army captured 129 wokou ships, burned 1,939 houses, killed 114 people, captured 21 people, and rescued 131 Chinese who the wokou had captured.

On 29 June, they burned 15 wokou ships and 68 houses, killed 9 people, and rescued 15 people, including Chinese and Koreans, who had been held captive, but more than 100 soldiers were killed by wokou. On 3 July, the Korean army withdrew to Geoje Island and withdrew completely after giving up the re-landing and occupation of Tsushima because of the loss of Korean army and worsening weather. In the record of 10 July, the number of soldiers killed by wokou was rectified to 180. On the other hand, according to historical documents recorded by the Sō clan, the death toll of the Korean army was 2,500.