Last season's league runners-up Marseille, who decided to put their faith in signing young players, also brought in midfielder Mario Lemina, another U20 world champion, from Lorient just before the transfer deadline.
Local media reports said Marseille paid 15 million euros for the 20-year-old Thauvin, who signed a five-year deal on Monday. Lemina inked a similar contract.
"I'm very happy to join Marseille, my favourite club," Thauvin told the club's website.
Thauvin joined Lille in January from Ligue 1 Bastia but was loaned back to the Corsica club for six months and scored 10 goals in 32 league games during his first top-flight campaign.
The pacey forward, who won the under-20 World Cup with France this year, asked to be transferred to Marseille when he returned and did not play a single minute for Lille.
He missed training last week and Lille, who had turned down Marseille's first offers in June, agreed to reopen talks amid growing dressing room unrest over the winger's stance.
Thauvin, Marseille's most expensive signing of the close season, is one of four exciting prospects to join the club along with Lemina, who has played 14 league games for Lorient.
Fullback Benjamin Mendy, aged 19, and midfielder Gianelli Imbula, who was voted the best player in Ligue 2 by his peers at the age of 20 last season, signed from Le Havre and promoted side EA Guingamp respectively in the transfer window.
Marseille have also brought in France winger Dimitri Payet from Lille and forward Saber Khalifa from Evian TG.
As part of the Lemina deal, Marseille sold Raffidine Abdullah and loaned fellow midfielder Larry Azouni, two home-grown players, to Lorient.