Nicholas Irwin (1833 – April 19, 1896) was a Union Navy sailor in the American Civil War and a recipient of the U.S. military's highest decoration, the Medal of Honor, for his actions at the Battle of Mobile Bay. Born in 1833 in Denmark, Irwin immigrated to the United States and was living in New York when he joined the U.S. Navy. He served during the Civil War as a seaman on the USS Brooklyn. At the Battle of Mobile Bay on August 5, 1864, he "fought his gun with skill and courage" despite heavy fire. For this action, he was awarded the Medal of Honor four months later, on December 31, 1864.