Fifteen Years War may refer to:
Long Turkish War, 1591–1606 war between the Habsburg Monarchy and the Ottoman Empire Pacific War, conflicts involving Japan from the Mukden Incident in Manchuria in 1931 through the end of World War II in 1945
See also Mukden Incident, a false flag event staged by Japanese military personnel in Manchuria in 1931 Second Sino-Japanese War, conflict primarily between the Republic of China and the Empire of Japan in 1937–1945 First Peloponnesian War, 460–445 BC fighting between Sparta and Athens, along with allies on both sides Thirteen Years' War (disambiguation)