Nippon Yūsen Kabushiki Kaisha (日本郵船株式会社) (Japan Mail Shipping Line), also known as NYK Line, is a Japanese shipping company.

The majority of Japanese merchant ships, tankers, and liners sailed under the NYK banner in this period. Regular services linked Kobe and Yokohama with South America, Batavia, Melbourne, and Cape Town, with frequent crossings to San Francisco and Seattle. Other routes connected local Chinese cabotage vessels on the Chinese coasts and upper Yangtze River.

From 1924, all new cargo ships for NYK were motor ships. NYK introduced its first passenger motor ships in 1929, but continued to buy a mixture of steam and motor passenger ships until 1939.

In World War II, the NYK Line provided military transport and hospital ships for the Imperial Japanese Army and Navy. Many vessels were sunk by the Allied navies, and installations and ports were attacked from the air. Only 37 NYK ships survived the war. The company lost 185 ships in support of military operations in the Pacific.

 Before the war, NYK had 36 passenger ships; by the time of Japan's surrender only one, the motor ship Hikawa Maru, survived.