O’Sullivan will get further mileage in the rookie test that follows the race weekend, where he will share driving duties in the second FW45 with fellow Formula 3 graduate Franco Colapinto.
2021 Aston Martin Autosport BRDC Award winner O’Sullivan emerged as the best-placed of the four Williams juniors in the F3 series, logging four wins on his way to second place behind recent McLaren signing Gabriel Bortoleto.
The 18-year-old only just outscored Colapinto, who won twice and was only nine points adrift in fourth place. He will graduate to F2 with ART next year.
O’Sullivan passed the first step of qualifying for a free-practice only F1 super licence thanks to the points he accrued in FIA F3 and GB3, but he also had to complete 300kms in what the FIA regulations call “a representative” F1 car.
He achieved that when Williams arranged for him to drive Alpine’s A521 in a private test in Bahrain last month.
O’Sullivan had previously driven an F1 car, having completed 32 laps of Silverstone in an Aston Martin AMR21 in October last year as part of his Autosport prize.
He will replace Alex Albon in Abu Dhabi, while Logan Sargeant’s Bahrain debut counted as a rookie run with the other car.
Speaking exclusively to Motorsport.com, Williams team principal James Vowles said there was a possibility of looking outside for a driver to fill the FP1 slot should O’Sullivan not have qualified for a licence.
“There were options to put in others that weren't in the driver programme,” said Vowles. “But we very much actually focused on making sure that we put our own driver in the car, and not others, because that's the investment that we're making.
“In terms of Zak himself, while he is coming from F3, he has driven a F1 car before.
"He won the Aston Martin BRDC Autosport Award, and had a positive result in that. And to actually do this event, you have to do 300kms or so in an F1 car. It wasn't a Williams F1 car, it was an Alpine.
“But it's enough that it gives me confidence he'll perform very well. If you look at his season and how he is as an individual, he's a very intelligent driver who knows how to extract the most out of machinery.
"He knows that actually, he's not here to set a lap time. He's here to build his experience base as the result of it. And I think he's an incredibly capable driver, and deserving of this opportunity in Abu Dhabi.”
“I’m really excited to participate in FP1 at Abu Dhabi,” said O’Sullivan. “I can’t wait to get behind the wheel of the FW45 for the first time, and get some good mileage under my belt.
“In addition to that, I’m returning to the car for the post-season rookie test to further my development with the team. Huge thanks to Williams Racing for the opportunity and for putting their faith in me to drive the 2023 car.”
Colapinto, who will make his F2 debut in Abu Dhabi before his Williams rookie test run the following week said: “I am extremely grateful to Williams Racing for giving me the opportunity to drive an F1 car in only my first year in the Academy.
“I’ve been dreaming of this day since I was a kid and have been working really hard for this. To have this chance at the official young driver test is a real honour.
“Thank you to the team for entrusting me with the FW45. Being part of the Academy this year has opened my eyes in so many different areas and I feel ready to make this step. I can’t wait.”
The Argentine driver will also graduate to F2 next year, making his series debut in the 2023 season finale in Abu Dhabi with MP Motorsport before continuing with the team next year.