The 37-year-old Brazilian, who previously won in 2015 an 2017, joins Frankie Dettori and Ryan Moore as a three-time champion.
A suspension meant De Sousa had to sit out the meeting, but that did not dampen his joy after partnering 148 winners from 779 rides in Britain during the title period.
Watch Tom Stanley's interview with Silvester de Sousa at Ascot on Saturday.
He said: “It’s unbelievable to win the jockeys’ championship again. After a slow start at the beginning of the season, from halfway we really picked up and it was a good season in the end.
“It takes a lot of effort, but that makes it even more special. I don’t have a massive retainer, but I just try to pick up as many rides as I can and ride the right horses.
“Winning the Britannia on Ostilio was a very special moment for me at Royal Ascot.
“It means the world to be crowned the champion for the third time – I’m delighted.
“I’m off to Hong Kong for the winter, so I hope to spend four months out there. The plan is to be champion again next year so hopefully that happens.”
A potential challenger to De Sousa is Jason Watson, who has set his sights on being champion jockey after being crowned the Stobart champion apprentice.
Watson, 18, had his first winner only 17 months ago, yet rode out his claim earlier this month and chalked up 100 for the year at Redcar on Friday.
With his family joining in the celebrations as he collected the Tom O’Ryan Trophy, Watson reflected on his breakthrough year.
“It’s been unbelievable what I have achieved and I wouldn’t have done it without the help of my jockey coach John Reid,” he said.
“It’s unbelievable to be here today. My whole family are all so proud and it’s just great to be here.”
From May 5, when the Stobart champion apprentice race started, Watson started the last day on 77 winners from 462 mounts.
“It’s very important that jockeys are rewarded as it’s such a tough career and lifestyle and they deserve the recognition which these awards give,” said Watson.
“I’ve definitely surprised myself. I only had my first ride in March 2017 and my fourth ride was a winner (Salisbury, May 2017, aboard Many Dreams). I’m a realist and I didn’t think it would turn out quite like this.
“I’ve just tried to achieve what I can and try my hardest. I didn’t expect it go this well so I’m delighted.
“Winning the Stewards’ Cup aboard Gifted Master was a very special day for me and riding my 100th winner of the year at Redcar yesterday was unbelievable.”
Watson has ridden for powerful connections this term, including Godolphin, and he revealed that he will work for Saeed bin Suroor in Dubai throughout the winter.
“I’ve been very fortunate to ride for connections such as Godolphin, who are such big owners and so well thought of in the sport,” he said.
“I wouldn’t have got these rides without my agent Tony Hind, so massive thanks must go to him.
“I’m still with Andrew Balding, but I am going to Dubai this winter to work for Saeed bin Suroor for a few months, then I’ll come back.
“I want to be champion jockey next year. Hopefully, I’ll have some rides in Dubai.”