The Williams F1 junior, who won the 2021 Aston Martin Autosport BRDC Young Driver of the Year Award, will join the French outfit for his rookie campaign.
The 18-year-old spent two years in F3, first with Rodin Carlin, where he finished 11th scoring two podiums, before moving to Prema for 2023.
The Briton finished second to Gabriel Bortoleto, having taken the most wins of any driver with four.
O’Sullivan said: “I am delighted to join forces with ART Grand Prix for the 2024 FIA Formula 2 season. The team has clearly demonstrated it has all the attributes to win, so I cannot wait to get started.
“ART have already made me feel very welcome. 2024 is set to be an exciting year and I'm ready for the challenge.”
ART currently leads both the drivers and teams’ standings in F2, with Theo Pourchaire leading the championship. Victor Martins is fifth as the highest-placed rookie.
Team principal Sebastien Philippe said: “I’m delighted about the collaboration between Zak and ART Grand Prix.
Source: Autosport