Mercurius of Transylvania

Mercurius (Merkúr) was a Hungarian distinguished nobleman and perhaps the first known voivode of Transylvania, who held the office during the reign of Coloman, King of Hungary. Two royal charters issued in 1111 and 1113 mention Mercurius as "princeps Ultrasilvanus", but he may have been only an important landowner in Transylvania without holding any specific office. The title voivode was first documented specifically in 1199.

A source from 1097 also mentions a "Mercurio comes Bellegratae", which means "count (ispán) of Fehér", and this record may point to the same person.