USS R-26 (SS-103) was an R-class coastal and harbor defense submarine built for the United States Navy during World War I.

The R-boats built by Lake Torpedo Boat Company (R-21 through R-27) are sometimes considered a separate class from those of the other builders.

[1] For surface running, the boats were powered by two 500-brake-horsepower (373 kW) diesel engines, each driving one propeller shaft.

Given hull classification symbol SS-103 in July, she spent her entire career operating out of Coco Solo.

Interrupting her service in those waters only for overhauls at Balboa and on the East Coast, she returned to the United States for inactivation in January 1925.