The 20-year-old made the squad after featuring in three warm-up games and, while he is behind the likes of Damian Penaud and Gabin Villiere in the pecking order, all eyes will be on the Bordeaux-Begles player when he starts against Uruguay in Pool A.
Bielle-Biarrey has only played 28 matches in the French Top 14 since his debut in January 2022 as he also pursues business and administration management studies.
"I've got some catching up to do. When it comes to studying, it's obviously more complicated. It's going to take a little longer, but I intend to see it through," Bielle-Biarrey told reporters on Tuesday.
At Lille's Pierre Mauroy stadium, Bielle-Biarrey, who also plays at fullback, will be 80 days younger than Romain Ntamack when the flyhalf made his World Cup debut in Japan in 2019.
"It doesn't mean much to me. I'm happy to hear it, but it's not going to help us become world champions.
"Obviously I'm very happy (to start). Everything's happened so fast for me. I don't really realise."
Bielle-Biarrey has quickly adapted to being in a world-class 33-man squad after going through the whole preparation, making the cut from a group of 42.
"Emilien (Gailleton, also 20) was there during the camps. We shared a room, and that helped us both integrate. Now we're a group of 33, we all have different roles but we're all involved," said Bielle-Biarrey.
"The competition is long so we're all focused on being ready when we're needed."
