Last week Honda announced that it had agreed to part ways with the eight-time world champion mutually at the end of the season, despite Marquez being contracted for next year.
Marquez, who won all six of his premier class titles with Honda having spent the last 11 years with the Japanese marque, has been heavily linked to Gresini for some time.
Honda’s efforts to retain Marquez, which included a recruitment drive to snare European engineering talent to help improve its bike, ultimately came to nothing.
HRC’s announcement all but paved the way for Marquez’s Gresini switch, though the Ducati satellite squad remained silent until Thursday when it formally confirmed the Spaniard’s appointment.
“This is a historical moment for the Gresini Family," team boss Nadia Padovani said.
"The fact that Marc Marquez chose to race with us in the upcoming season is absolutely fantastic and I’m extremely happy to be able to make it official.
"In less than a season we got really close to his brother, and we’ll welcome Marc the same way, as we’re sure he has all the potential to be competitive on the GP23 from the get-go.
"Last but not least, I would like to thank Fabio Di Giannantonio for his professionalism, and we wish him all the best for the continuation of his career.”
Gresini’s announcement was always thought to coincide with this weekend’s Indonesian Grand Prix, with the team having sponsors from the country.
Gresini had wanted Marquez to sign for two years, but he only wanted a one-year deal to keep his options open for the 2025 campaign when most factory seats go up for grabs.
It’s because of this that Marquez will not be able to take any of his current Honda team with him, with Ducati wary of rival engineers potentially leaving in 2025 and taking its bike secrets with them.
Marquez will reunite with his younger brother Alex at Gresini next year on 2023-spec Ducatis, having briefly been team-mates in 2020 before the former was forced to sit out the entire campaign with a serious arm injury.
Alex Marquez made a similar move from Honda to Gresini Ducati this year and enjoyed a grand prix podium in Argentina, before taking a sprint victory at the British GP.
On Tuesday, Autosport revealed that RNF Aprilia’s Miguel Oliveira is top of Honda’s hit list to replace Marquez at the factory squad next year.
The five-time grand prix winner is currently contracted to Aprilia for 2024, but is thought to have a clause in his contract that stipulates he can leave ahead of this if a factory team offers him a deal.
Aprilia has refuted this, however, while Oliveira insists there has been no approach from HRC.
