Brownlee dropped from British triathlon team for Olympics
Jonny and older brother Alistair have been mainstays of the sport in Britain for more than a decade, with five Olympic medals between them.
Alistair made his Games debut in 2008 before winning gold on home soil four years later in London.
He successfully defended the title in Rio, while Jonny took bronze in 2012, silver in Rio and a gold as part of Britain's relay team in Tokyo three years ago.
His performance in that race led Jonny Brownlee to reverse his decision to retire from Olympic competition in a bid to make one further appearance in Paris.
But the 34-year-old's results since Tokyo have been disappointing and he has missed out on the second men's place in the British team, with debutant Sam Dickinson, 26, chosen alongside Tokyo silver medallist Alex Yee.
"I have not been selected for the Paris 2024 Olympic Games," Jonny Brownlee wrote on Instagram.
"The Tokyo mixed team relay was one of the many highlights of my career and I still believe I could have helped Team GB win another medal in Paris."
He added: "I will be supporting the Team in whatever way I can and really hope they go on to defend the title!
"I have achieved more than I could ever have imagined in my Olympic career. After 99 world triathlon starts, 52 podiums and 3 Olympic medals, it's not the fairytale ending that I'd wished for, but Paris was always a bonus, and it can be the unwritten chapter of an incredible book!
"I have a great summer to look forward to and some exciting racing ahead."
Performance director Mike Cavendish, speaking to Britain's PA news agency, said: "There's no doubt that, had we decided to pick Jonny, he would have still done a brilliant job. We're just faced with having to make some really difficult decisions and we've got an athlete in Sam who just edged it this time."