Mathieu Daneau was 24 when he was last seen on May 3, 2007, in Saint-Hyacinthe, Quebec. The last known location for Mathieu was the Honoré-Mercier hospital, and that detail has been central to the timeline of his disappearance.

The Sûreté du Québec for the MRC des Maskoutains issued a missing person bulletin describing him as a white, French-speaking male with short brown hair and brown eyes. Authorities asked the public for any information and have periodically reissued their appeals; the investigation has remained open but few public updates about progress have been released.

Mathieu disappeared from a place of care and his family continues to seek answers. If anyone was in or near Honoré-Mercier hospital on or around May 3, 2007, or has seen Mathieu since then, please report what you know to the Sûreté du Québec.