Rennes have made their second midfield signing in as many days with the capture of Sanjin Prcic from Sochaux.
Lazio's new centre-back Stefan De Vrij has denied Manchester United were ever in the hunt to sign him.
The 32-year-old centre-back, who can number Chelsea, Stuttgart and Sporting Lisbon among his former clubs, has signed a one-year contract at De Kuip after leaving Brondby.
A statement published on Feyenoord's official website revealed Boulahrouz's deal in Rotterdam includes the option of a further year.
He left RKC Waalwijk for Hamburg in 2004 and made 35 appearances for Holland across eight years.