The announcement came in an address by Carles Puigdemont to the Catalan regional parliament in Barcelona on Tuesday.
Catalans held an independence referendum on October 1 and secured a 92 percent vote in favour of separating from Spain. A unionist boycott of the vote meant turnout stood at just 43 percent.
“Based on the results of October 1st, Catalonia has earned the right to be an independent country and has earned the right to be listened to and respected,” Puigdemont said in his speech.
“The ballot boxes are telling us the people are in favour of independence and that is the path we follow.
“By being the president, I assume my responsibility to declare that Catalonia should become an independent state in the form of a republic.”
Puigdemont then asked parliament to suspend its mandate to immediately declare independence so that dialogue could begin.
Reports said Catalan leaders signed a “symbolic” declaration of independence on Tuesday but immediately put it on hold and called for talks.
Puigdemont and his allies signed the declaration outside the parliament chamber, but he then suspended it and again called for dialogue, reports said.
A Spanish government spokesman told AFP news agency that it is “unacceptable to make a tacit declaration of independence to then suspend it in an explicit manner”.
Mariano Rajoy, Spain’s prime minister, is to chair an emergency cabinet meeting on Wednesday to discuss the central government’s response.