Monaco continues to build towards the 2018-19 Ligue 1 season by completing the signing of Pele.
The 26-year-old joins from Rio Ave and is likely to replace Fabinho following the midfielder's move to Liverpool.
Pele, a Guinea-Bissau international, won Rio Ave's player of the season award last campaign.
"I am very happy to join Monaco, an ambitious club competing in the Champions League and a contender in Ligue 1," Pele told the club's official website.
"It's great motivation and a dream to represent Monaco. I cannot wait to meet the staff and my team-mates."
Although Fabinho and Thomas Lemar have left the club, Monaco has made signings including Barcelona teenager Robert Navarro and Chelsea youth prospect Jonathan Panzo for the new season.
They follow Monaco's signing of Willem Geubbels, a France Under-17 international who joined in a €20million deal from Lyon last month.