The announcement on Friday follows weeks of negotiations after new Lille coach Marcelo Bielsa identified the 25-year-old as a priority transfer target, reports Xinhua news agency.
"The contract hasn't been signed but we have reached an agreement by email and telephone," Sao Paulo football director Vinicius Pinotti was quoted as saying by the Folha de S.Paulo newspaper.
"We received a proposal three weeks ago. It wasn't our intention to sell him but Thiago's wish was to leave and we don't want to hold on to players who don't want to be here," he added.
Mendes made 145 first-team appearances for Sao Paulo after his 2015 move from Goias.
"It was my choice. The club tried to keep me and I had the support of everybody there but I want to play in Europe. I appreciate everything that Sao Paulo did for me over the past three years," the Brazilian said.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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