The singer received the accolade at a ceremony attended by dignitaries on Tuesday.
Williams brought his pregnant wife Ayda Field and his 22-month-old daughter Teddy to the event, along with his parents, Jan and Peter, who he kept the event a surprise from until they arrived at the Town Hall.
He said: "I am delighted to have received the great honour of the Freedom of the City of Stoke-on-Trent.
"It's been a special day for Ayda and I and I am very grateful to those involved, especially to The Lord Mayor, for this honour."
He was presented with an honorary scroll by Lord Mayor Majid Khan and the council's chief executive John van de Laarschot also attended. The star then signed the roll of honorary freemen, which includes one of his footballing heroes - Sir Stanley Matthews.
Williams, who was clearly touched by the accolade, said: "There is a saying that it takes a village to raise a child. This particular village moulded me into the man I am today. I wear where I am from as a badge of honour. So to have that honour returned to me is very special.
"I'm proud of our six towns. I'm proud to come from Stoke-on-Trent. I'm extremely honoured and grateful that you think it's fitting to give me this recognition. God bless you all."
He also took his wife and daughter to see the blue heritage plaque which was put up in Victoria Park during a series of celebrations to mark his 40th birthday in February.
The family watched a short film at today's ceremony including highlights of the event, which was organised by Stoke local paper The Sentinel, and included performances, street parties and a bus tour.
Williams said afterwards: "It meant so much to me that I was able to visit Stoke privately today with my family - it's the first time Teddy has been and we got to visit the Town Hall and to see the plaque in Victoria Park."
His father Pete, who attended with his wife Mel, said: "This is an incredible moment. Rob has won so many awards but there's been nothing like this. He's from a family born and bred in Stoke-on-Trent and this is a huge day for us. It's very poignant, very moving."
And Williams's mum Jan, said: "I'm so proud of my son. I always knew he was very special. It sounds strange to be saying this but I always felt he was going to make something of himself and he really has. He's a wonderful man and this is a very special day for him."
Robbie said he was saddened that his grandmother Betty was not there to see it.
"This would have been something for her," he said. "She was so proud of her city. I really thought a lot about her today.
"I didn't actually know what to expect. I actually get very anxious about public ceremonies but the room was filled with such warmth and pride, it was very unshowbiz and I felt incredibly relaxed.
"It's very surreal to feel I've got this huge honour and I haven't totally taken it in. But it's so poignant for me to have my little girl with me and my wife and my unborn baby.
"This is Teddy's first visit to Stoke, I grew up here - her life is so different to mine. At her age Stoke-on-Trent was my whole world and I dreamed of getting into another world. All my dreams came true but as they come true you realise how much you miss the freedom you had as a kid and the safety and security you feel in your own little world.
"Stoke-on-Trent made me. My humour, my 'cheeky chappie' bit, that's all from here. Cut me and it's through me like stick of rock."