Surfer and environmentalist Chris Homer said it was a "wonderful" feeling to have won the trust of the voters to lead the city.
A surfer and environmental activist, Mr Homer officially declared the winner over Labor incumbent Marianne Saliba, who said she was still "perplexed" as to why she was voted out.
Mr Homer won with 24,434 first preference votes, defeating Ms Saliba 52.8 per cent to 47.2 per cent.
"The first gift has been delivered, and that's a whole new fresh wave of leadership, and a whole new paradigm of leadership on council," Mr Homer said.
"The next priority is making sure all the councillors in all the wards, no matter what their political persuasion, can deliver in an equitable and non-partisan, inclusive way.
"I'm looking forward to having a council that delivers to all parts of the LGA, including west of the coast, equitably."
Mr Homer rode a wave of popular opposition to increased development of the Killalea State Reserve, which succeeded in having - on the eve of the election - Killalea announced to be soon becoming part of the National Parks estate.
Marianne Saliba said on Monday she was still perplexed as to why she was voted out.
"It's mixed emotions - this is democracy," she said. "I guess I'm a little perplexed about why. Change for the sake of change isn't necessarily a good change.
"I think my opponent only had one policy and that was new leadership, and Killalea - he wasn't the only person who worked on it. There were a lot of people involved in saving Killalea."
Ms Saliba is now out of council after nine years, as she did not run for a councillor position in any of the wards.
"It's only a two year and nine month term and I'll wait until it gets closer and then determine whether I'll run again," she said.
"You haven't seen the last of Marianne Saliba no matter what I end up doing.
"I have a passion for my community. I've been approached by lots of different groups within Shellharbour and further abroad where I have assisted in linking the community to these other groups.
"Don't be surprised if I pop up somewhere else instead because that passion is not going to go away."
She admitted the result surprised her.
"It was definitely a shock," she said.
"It almost seems like the tall poppy syndrome - it's an Australian pastime. We build somebody up and then we chop them down. I can't say there was any one issue that people were strongly being vocal about.
"My record, I would have to say, speaks for itself. First of all it was about financial sustainability, it was saving Shellharbour from a merger with Wollongong, it was getting Shellharbour back on the list of regional councils to get funding, regional funding for the airport, $16 million.
"I've got a lot of things that I'm very proud of in Shellharbour - having the airport named the Shellharbour Airport because the people of Shellharbour are responsible and financially it's theirs."
Ms Saliba named saving Shellharbour from amalgamation with Wollongong City Council as her top achievement.
"That I took very personally - I felt like I was carrying the weight of the city on my shoulders during that," she said.
"I didn't to it on my own - I did it with my colleagues and council staff and the community. But there had to be somebody strong leading it."
Asked if she had congratulated Mr Homer, Ms Saliba said they spoke last week as well as on Monday..
"Chris came to visit me last week and brought me some flowers and a bottle of bubbly," she said.
"I said 'Chris would you like a hug?' and I embraced him, and congratulated him.
"What I did say to him is that it's not a nine-to-five job. It's when people are ringing you up at 11 o'clock at night because there's dogs barking, or someone trying to break in, or cars speeding up and down their roads, or during holidays seasons where people have more time than they need and they are on social media looking for someone to hammer - then he will know, he will understand what type of job it is."
- Homer wins mayoralty
- Chris Homer declared victor in Shellharbour
- Won 52.8pc of vote
- Marianne Saliba off council
- Council seats declared tomorrow