山本五十六（日语：山本五十六，1884年4月4日－1943年4月18日），旧日本海军军人，曾留学美国哈佛大学，第二次世界大战期间担任日本海军联合舰队司令长官。

山本五十六在日本海军中历任重要职位，进行了多项重大变更与改革，尤其是亲手组建了日本海军航空兵部队。在太平洋战争早期担任日本海军联合舰队司令长官并策划或指挥了数次战役，例如珍珠港事件以及中途岛战役。山本在搭乘飞机前往所罗门群岛前线视察的路上遭美军P-38闪电式战斗机拦截，座机（一式大型陆上运输机）被击落。山本之死对日本军队士气造成了沉重打击。

Isoroku Yamamoto(山本 五十六,Yamamoto Isoroku, April 4, 1884 – April 18, 1943) was a Japanese Marshal Admiral and the commander-in-chief of the Combined Fleet during World War II until his death.

Yamamoto held several important posts in the Imperial Japanese Navy, and undertook many of its changes and reorganizations, especially its development of naval aviation. He was the commander-in-chief during the decisive early years of the Pacific War and so was responsible for major battles such as Pearl Harbor and Midway. He died when American codebreakers identified his flight plans and his plane was shot down. His death was a major blow to Japanese military morale during World War II.