The ruling Law and Justice (PiS) party failed to secure parliamentary majority.
What does this mean? Most likely, the new coalition government will be led by the pro-EU Civic Coalition.
Poland won, democracy has won," Mr Tusk, 66, told a large crowd of jubilant supporters in what felt like a victory rally in Warsaw. "This is the end of the bad times, this is the end of the ruling party, PiS."