Military conflict between the United States of America and Mexico from 1846 to 1848

1840 United States presidential election — 14th quadrennial U.S. presidential election

Indigenous Australian Frontier War

1840 battle between Zulu factions

Battle in February 1840

1840 siege during the Russo-Circassian War

1840 battle between China and Britain

1840 battle fought at this river

1840 treaty leading to the Oriental Crisis

1840 battle between Egypt and the Ottoman Empire

1840 treaty between the United States and Miami