Wollongong Lord Mayor Gordon Bradbery was hospitalised with a heart attack over the weekend and will be taking leave to recover.
Wollongong City Council staff and other councillors shared the news of his heart attack on Monday, and wished the popular city leader well.
The council also said Cr Bradbery, 68, was expected to make a full recovery and that he was resting up following surgery.
Wollongong City Council General Manager, Greg Doyle, said he had spoken with Cr Bradbery and passed on the thoughts and best wishes on behalf of council and the community.
"We will continue to support him as he recovers and while the Lord Mayor and his family focus on his health, Councillor Tania Brown will fulfil the duties of Acting Lord Mayor," the council said.
Cr Brown, who will take the reins at next weeks' council meeting, said she hoped he would be back in the chair as soon as possible.
"I, and my fellow Councillors, were upset to hear of Cr Bradbery's heart attack and wish him a fast recovery,'' she said.
"Cr Bradbery is well-loved and regarded in Wollongong and this has come as a shock to us all.
"I have no doubt, he will be back in the office as soon as possible, and in the meantime we will continue to do the best for our city."
On Friday night, Cr Bradbery attended the 118th Windy Gully Memorial at Mount Kembla, joining other community leaders to speak at the service.