Today celebrates the life and achievements of Martin Luther King Jr., an influential American civil rights leader. He is most well-known for his campaigns to end racial segregation on public transport and for racial equality in the United States. The Day (officially Birthday of Martin Luther King, Jr., and sometimes referred to as MLK Day) is an American federal holiday marking the birthday of Martin Luther King Jr. It is observed on the third Monday of January each year, which is around King’s birthday, January 15.