Baron Tsuboi Kōzō (坪井 航三, 7 March 1843 – 1 February 1898) was an admiral of the early modern Imperial Japanese Navy, known primarily for his role in the First Sino-Japanese War.

Witnessing firsthand the firepower and devastation caused by a relatively few Western warships, Tsuboi became convinced Japan must also obtain this weaponry to survive.

That same year he received training on board the flagship USS Colorado of the American Asiatic Squadron and was sponsored by Admiral John Rodgers to attend Columbia University from April 1872 until July 1874.

From 1875 through 1879, he surprised warship construction at the Yokosuka Naval Arsenal; however, he was injured in an accident in August 1878 which required two months hospitalization.

A national hero following the war, Tsuboi was ennobled with the title of danshaku (baron) under the kazoku peerage system on August 20, 1895, and promoted to vice admiral the following year.