Governor Ram Naik approved the name change on Friday.
The Uttar Pradesh government has issued a notification directing its departments to use Prayagraj instead of Allahabad for all official purposes, district magistrate Suhas L Y said today.
Governor Ram Naik approved the name change on Friday and the order comes into force with immediate effect, he said.
However, it will not have any bearing on cases already in the courts, according to a release from the magistrate's office.
The proposal to rename the historic city of Allahabad as Prayagraj was approved by the Uttar Pradesh Cabinet on Tuesday.
The decision was taken at a cabinet meeting presided over by Chief Minister Yogi Adityanath, who had said this was in keeping with the wishes of the people. "The BJP government has rectified the mistake made by Akbar," a state BJP spokesperson had said.
Earlier, opposition parties, including the Samajwadi Party and Congress, criticised the decision, which comes ahead of the Kumbh Mela in January next year.
Congress spokesperson Onkar Singh had said that the region where Kumbh is held is already called Prayagraj and if the government is so eager, they can make it a separate city, but the name of Allahabad should not be changed.
The UP chief minister had dismissed the Opposition's criticism saying, "Those who are opposing this are not aware of their history, culture and traditions and we can't have hopes from them."