More than 100 pro-European protesters died during the demonstrations which brought down the former president and led to the crisis in the east of the country.
Rosary beads were hung from trees and clergymen said prayers during the event to commemorate those who died in the uprising that toppled Moscow-leaning Viktor Yanukovych's government.
Thousands of flowers were laid at the site where they were killed and a minute's silence was held before crowds sung the national anthem.
New President Poroshenko said the activists' deaths were not pointless and it was the start of a fight against the "fear, panic and mistrust" that "a neighbouring country" was trying to create in Ukraine.
"The revolution was a first, and most importantly, victorious battle in the war for our independence," he said.
