"The Governor, in exercise of the power conferred on him by Article 164 (1) of the Constitution of India has been pleased to issue the order appointing Mamata Banerjee the chief minister of the state of West Bengal," a Raj Bhavan release said.
Narayanan had yesterday sent a letter to Banerjee inviting her to form the government following her party's landslide victory in the Assembly elections.
On Sunday, the Trinamool Congress had formally staked claim to form the government shortly after Banerjee was elected its Legislature Party leader.
Partha Chatterjee, the newly-elected Deputy Leader of the TC Legislature Party, had said yesterday that the Governor's invitation had been received by the party.
While staking claim to form the government, a list of 184 TC legislators was submitted to the Governor.
Trinamool's ally Congress has already submitted a letter of support to the government to be formed under Banerjee's leadership.