Union Day

Union Day may refer to:
 * "Great Union Day" on December 1, also known as "Unification Day", the national holiday of Romania
 * "Union Day" on February 12 in Myanmar, commemorating the anniversary of the Panglong Agreement in 1947
 * "Union Day" on April 26 in Tanzania, commemorating the unification of Zanzibar and Tanganyika in 1964