The German driver will drive for PHM Racing by Charouz this season and is part of the French team’s Rac(H)er programme, which hopes to boost diversity within Alpine.
It will also provide resources and training with the aim to fielding a female driver in Formula 1 in the future.
She is the third Alpine Academy member on the 2023 grid, alongside Hitech Pulse-Eight's Gabriele Minì and ART Grand Prix's Nikola Tsolov.
Ahead of her return to F3, Florsch said: “I am really excited and very happy to return to FIA Formula 3 this season with PHM Racing by Charouz.
“My goal has always been to race with the best of the best.
“Since the beginning of my career, I have been working very hard towards this goal every day with my team in the background.”
Florsch began her single-seater career in 2016 after success in Ginetta Juniors, driving in the ADAC Formula 4 Championship and becoming the first female to score points in the series.
She moved to European F3 in 2018 and went on to finish seventh in the Formula Regional European Championship.
Her first F3 stint came in 2020, driving for Campos Racing, before a move to sportscar racing where she participated in the Le Mans 24 Hours, the World Endurance Championship, European Le Mans Series and DTM.
Asked about the signing of Florsch, Alpine F1 team principal Otmar Szafnauer added: "Well, let's see how she goes this year. She'll be competing against the boys in a very competitive formula. F3 is not easy. So we're going to help her to achieve."
Florsch will drive alongside Piotr Wisnicki and Roberto Faria at the newly renamed PHM by Charouz team this season.
“I have lots of respect for Sophia's decision to come back to Formula sports and to take the challenge in this competitive field said team Manager Roland Rehfeld.
“She is very experienced in professional Racing in various classes and has a very professional attitude and working style.
“The racing world so far helped her to become even more ambitious and focused than many other male drivers.
“That’s another fact, why we start with Sophia. With our new campaign as PHM Racing by Charouz, we will do our best to support her on her path to the top.”
