Tsutomu Sakuma (佐久間 勉, Sakuma Tsutomu, September 13, 1879 – April 15, 1910) was a career naval officer in the Imperial Japanese Navy, and a pioneer submarine commander, known primarily as the commanding officer during the sinking of Submarine No.6.

He subsequently served with the 15th Torpedo Boat Flotilla, and was on board the cruiser Kasagi during the Battle of Tsushima on May 26, 1905.

After completing the torpedo warfare school, Sakuma served on the submarine tender Karasaki and was later a squad leader on the Japanese cruiser Tsushima.

On April 15, 1910, while engaged in a practice dive in the Inland Sea off of the coast of Yamaguchi Prefecture, the submarine suffered a malfunction resulting in the loss of the ship and crew.

The journal was posted in later press reports, and Sakuma became a posthumous national hero and an example for courage and steadfastness within the Imperial Japanese Navy.