The Supreme Commander-in-chief of the Imperial Japanese Army and Navy (Japanese: 大元帥陸海軍大将, romanized: Dai-gensui-riku-kai-gun-taishō) was the highest rank of the Imperial Japanese Army and the Imperial Japanese Navy from 1872 to 1945, when the Empire of Japan was dissolved. The rank of dai-gensui was the highest rank in the Imperial Japanese Armed Forces and was held solely by the Emperor of Japan in his capacity as Supreme commander-in-chief. It formally became obsolete in 1945 when the Imperial Japanese military was abolished.

The term originated from the Chinese military title da yuan shuai (大元帥), a title higher than yuan shuai (元帥, pronounced gensui in Japanese).

Decree No. 252 by the Dajokan, dated 7 September 1872, formally recognized the rank of dai-gensui; however, no appointments were made before the rank was abolished along with that of gensui on 8 May 1873. According to "Draft Ordinance No. 142" of the Constitution of the Empire of Japan (Chapter 1 Part 1) issued on 30 September 1889, the Emperor was officially granted the rank of dai-gensui and designated as supreme commander of the Army and Navy.

The kanji characters also refer to a Buddhist deity, Daigensui Myō'ō (大元帥明王), a Wisdom King worshipped by the Imperial Court since Emperor Ninmyō and by the Shingon sect, for its legendary miraculous power to quell foreign enemies and rebellions, much like a military leader.

The insignia for the rank of dai-gensui were similar to those of an Imperial Japanese Army General or Imperial Japanese Navy Admiral, distinguished by the addition of the gold imperial chrysanthemum emblem.