He failed to convince the ruling Armenian party a week ago to support him, but opposition leader Nikol Pashinyan has now won parliamentary support for assuming the post of prime minister of the country.
Mr. Pashinyan headed weeks of protests End of Serzh Sargsyan's ten-year reign
Speaking to parliament on Tuesday, thousands of supporters gathered in the capital, Yerevan.
Rock star Serj Tankian had joined the crowd on the eve of the vote.
Mr. Pashinyan, who led the so-called "Velvet Revolution" of Armenia, promised MEPs that human rights would be protected and that corruption and electoral manipulation would end.
"All people are equal before the law, there will be no people enjoying privileges in Armenia, that's it, full point," he said.
Mr Pashinyan's party colleagues spoke in Parliament about a "historic day". Lena Nazaryan told MEPs that the revolution was a culmination of two decades of despair and struggle. "The police are free now," she said. "School teachers are free, local administrations are free."
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The evening before the vote, we stood next to Mr. Pashinyan. Mr. Tankian – the lead singer of the American-Armenian heavy metal band System of a Down – praised the demonstrators in Armenian before leading them in a traditional song. The songs of his group have been played regularly at rallies since protests began on April 13th.
How did we get here?
After ten years in power, Sargsyan left Armenia's presidency last month, only to be elected prime minister by a parliament controlled by his Republican party.
Mr. Sargsyan's decision was seen by critics as a way to cling to office. Under a 2015 referendum that was marked by irregularities, Armenia shifted power from the presidency to parliament.
Mr. Pashinyan, who had begun a protest march to Yerevan before the President's change to the Prime Minister, came to the capital to hold daily protests.
On April 22, he held a brief meeting with Mr. Sargsyan, but was arrested when the talks collapsed. He was released the following day and Mr. Sargsyan resigned six days after his election as Prime Minister.  On May 1, a parliament dominated by the ruling Republican Party rejected Mr. Pashinyan as prime minister, although he was the prime minister only candidate. The following day, a general strike took place in Armenia, and eventually the republican MPs said they would support him in a vote on 8 May.
Armenia's peaceful revolt against one-party rule is considered unprecedented in the former Soviet Union. Russia has a military base in Armenia, but has not intervened there.