The Premier League side have agreed a deal for the 24-year-old, who will make the move to the King Power Stadium on 9 June, when the transfer window formally opens.
Pereira, who will travel to Russia in summer, after being named in the Portugal squad, completed a medical and finalised terms on Saturday. The full-back, who can also play as a winger, has worked with Claude Puel previously, when the pair were at Nice together.
Speaking after the deal was confirmed, the Leicester manager said: “I’m delighted to have a player of Ricardo’s quality on board for next season, I remember him well from my time at Nice.”
Ricardo expressed his satisfaction at the deal, in an interview with the club's website.“I feel very happy to be here and I can’t wait to do my best to help the team," he said. "The atmosphere, the fans and the football of the Premier League makes it the best in the world. I am here to support the team and to help the club to achieve its goals.”
Ricardo made 43 appearances for Porto this season, as the club clinched their 28th Portuguese league title.
May 19, 2018