Thousands of people gathered at a Yerevan memorial to remember the up to 1.5 million Armenians who were killed in World War I-era Ottoman Turkey.
Armenian President Serzh Sarkisian and the head of the Armenian Apostolic Church, Catholicos Garegin II, attended ceremonies marking the event.
"Today we bow to the memory of innocent victims," Sarkisian said in a statement.
President Barack Obama said in a statement that the United States stood "with Armenians everywhere in recalling the horror" of the massacres.
Armenia points to the tragedy as being one of the first examples of genocide in modern history, predating the Holocaust committed against Jews by Nazi Germany in World War II.
Some countries have publicly condemned Turkey for the atrocities committed at the start of the last century, but Turkish authorities point out that many Turks were killed in the conflict also and deny there was any systematic campaign to exterminate ethnic Armenians.
Based on reporting by ITAR-TASS and Interfax