America's Cup sloop Shamrock III. Shamrock III was entered in the 1903 America's Cup by Scottish selfmade millionaire Sir Thomas Lipton, founder of the Lipton tea company. The 12th America's Cup was the third consecutive Cup to be unsuccessfully challenged by Lipton - first in 1899 with Shamrock, and again in 1901 with Shamrock II. The third Shamrock, as well as the first, was designed by William Fife. Lipton made two more unsuccessful challenges on the Cup, in 1920 with Shamrock IV, and again in 1930 with Shamrock V.

In 1903, Shamrock III lost to the American sloop Reliance.

The mast of the Shamrock III lives on a flagpole in front of the Central branch of the Brooklyn Public Library.