Armenian Prime Minister Tigran Sarkisian resigned Thursday, the deputy parliament speaker told AFP, saying the premier had been looking to leave his post for a month.
Sarkisian, who had been prime minister since 2008, said on his Facebook page that the decision was "deeply thought-out".
His government had come in for sharp criticism since the January 1 launch of a contentious pension scheme, which requires people born after 1974 to deposit five percent of their pay in private retirement funds.
Demonstrations against the measure have drawn thousands of protesters into the streets.
"He had submitted his resignation letter a month ago, but the president only accepted it today," said deputy speaker Eduard Sharmazanov.
He said President Serzh Sargsyan had kept Sarkisian in his post because of Armenia's negotiations on joining a Russian-led customs union and a Constitutional Court ruling on the pension system.
A landlocked Caucasus country of 3.2 million people that was badly hit by the global downturn, Armenia is economically isolated because its borders with neighbours Turkey and Azerbaijan have long been closed over political disputes.
Sarkisian surprised many last year by turning his back on years of negotiations toward a free-trade deal with the European Union in favour of joining the Moscow-led customs union, a pet project of Russian President Vladimir Putin.