The Marca Geronis ("march of Gero") is a vast super-march in the middle of the tenth century.

It is created probably for Thietmar (in the 920s) and passed to his two sons consecutively: Siegfried and Gero.

On Gero's death in 965 it is divided into five (sometimes six) different marches: the Nordmark, the Ostmark, Meissen, Zeitz, and Merseburg.