Those watching the star-studded catwalk show at Brooklyn's Barclays Center were not allowed to post photos before Amazon streams it from 20 September.
The event featured music stars like DJ Khaled, Halsey, Big Sean and Migos.
"You have no idea how crazy of a show is coming," tweeted the Barbadian star.
The 31-year-old singer-turned-designer attempted to "blend music, fashion and culture", with "special appearances" from models like Bella and Gigi Hadid, Normani and Cara Delevingne.
My phone was just put in a sealed bag by Amazon for the duration of the @rihanna Fenty show and I am... so grateful.
According to W Magazine, the Amazon deal was "taking fashion week into the streaming era".
Variety's Elizabeth Wagmeister wrote: "The show was unlike anything previously staged during Fashion Week - and possibly anywhere."
The Daily Mirror's fashion commentator Amber Graafland said she thought fashion show promotion on this scale was unprecedented. Rihanna was focusing attention back on the catwalk rather than the rich and famous onlookers, she said.
"What's happened to the fashion show of late is it's all about who is there and it's the greatest show on Earth," Graafland told the BBC.
"Everybody wants the eyes of the world on their show. Now Rihanna has turned it into a piece of theatre, conceptualised it and is making people see it as she wants them to see it."
Commentators compared the buzz around Rihanna's Amazon tie-up with the fortunes of Victoria's Secret, which is not staging a televised catwalk show for the first time in almost two decades after it hit a ratings low in 2018.
Victoria's Secret had been criticised for a lack of diversity, whereas one hallmark of Rihanna's Savage Fenty X fall/winter underwear range is its inclusivity, with the star saying she wants to "celebrate everybody".
Tuesday's show was choreographed by Parris Goebel, best known for her work on music videos such as Justin Bieber's Sorry.
Afterwards, Rihanna told Business of Fashion: "I love how she makes everything sexy despite society's ideal of what sexy looks. I don't care about any skinny Victoria's Secret model when I look at Parris. I want to be that woman on the inside."
Amazon Studios described the show as "a radical departure from tradition", with "exciting surprises around every corner".