Erdogan met Wednesday with his national security council and council of ministers, the latter of which approved the state of emergency recommendation.
"The purpose of the declaration of the state of emergency is, in fact, to be able to take the most efficient steps in order to remove this threat as soon as possible, which is a threat to democracy, to the rule of law and to the rights and freedoms of the citizens in our country," Erdogan said, according to a government translation, CNN reported.
Erdogan, speaking to a national television audience, said the state of emergency was not a threat to democracy. Governors will have expanded powers and the army will be under the command and control of the governors, the President said.
He guaranteed that all the "viruses" in the armed forces would be cleansed.
"It is very similar to a cancer," he said. "It is like a metastasis that is going on in the body that is Turkey. And we will clean it out."
The President praised the reactions to the coup attempt, in which 246 people died and 1,536 were wounded.
"Every member of our nation came together as one," he said.
Turkey has now fired or suspended about 50,000 people after a failed coup over the weekend as it intensifies its vast purge -- battering the country's security forces and many of its democratic institutions.