The symbol of Paris will be bathed in black, yellow and red light in homage to "the victims, their loved ones and all the people of Belgium," she said in a statement following the attacks that killed at least 26.
"Today Europe is targeted at her heart," Hidalgo said. "Once more it is basic values that are attacked: freedom, humanism, tolerance and unshakeable commitment to democracy."
She expressed her "full solidarity and that of Parisians," the statement said, adding that the mayor spoke to Brussels counterpart Yvan Mayeur to "tell him how much we share their sadness and grief.