A Ganerbenburg (plural: Ganerbenburgen) is a castle occupied and managed by several families or family lines at the same time. These families shared common areas of the castle including the courtyard, well, and chapel, whilst maintaining their own private living quarters. They occurred primarily in medieval Germany.

The German word ganerbe appears in the Middle High German romance, Parzival, written by Wolfram von Eschenbach around 1200. The legal term Ganerbschaft appears from textual evidence to go back at least to the second half of the 9th century. In Old High German, gan meant "common", "joint" or "commoner". Accordingly, the term Ganerbenburg may be roughly translated as "common inheritors' castle". The first historically verifiable Ganerbschaft arrangement appears in the 13th century in Alsace at the castle of Haut-Kœnigsbourg.

Ganerbenburgen often came about as a result of a type of inheritance known as a Ganerbschaft ("Common/Joint Inheritance"). Each branch of the family built, usually, their own residential building within a common curtain wall. Sometimes these residences were expanded into independent castles in their own right within the common castle site. Ganerbenburgen also resulted from the sale of parts of a castle in times of financial hardship or through the pledging or enfeoffment of an element of the castle.

The castles of powerful feudal lords were often planned from the outset as Ganerbenburgen. Each castellan or Burgmann was responsible for the management and defence of a sector of the castle. This was not just for practical reasons; the higher nobility naturally wanted to limit the power of their liegemen (Dienstmannen). A good example of this is the Franconian castle of Salzburg near Bad Neustadt an der Saale, a castle enfeoffed (Lehensburg) by the Würzburg bishops.

Ganerbenburgen that had evolved were sometimes forced to submit to the suzerainty of more powerful feudal lords. The Würzburg chronicler, Lorenz Fries, mentioned three such examples in his bishop's chronicle. In 1458, the joint lords of Steckelberg Castle near Schlüchtern refused access to the bishop and attempted to modernize the castle fortifications. Bishop John III of Grumbach eventually asserted his authority after a military conflict.

In 1478, despite an imperial mandate, the mighty imperial city of Nuremberg had to acquiesce to Count Palatine Otto II of Mosbach selling Rothenberg Castle above Schnaittach to a community of 44 Franconian knights. This group of knights wanted to build a strong bulwark against competition from the rich citizens, who they deeply mistrusted. Significantly, the higher nobility were denied co-ownership; only the most important Franconian families from the lesser nobility were permitted to participate in joint ownership.

A legal requirement for the establishment of a Ganerbschaft was the enfeoffment of the castle estate to the gesamten Hand ("whole hand"), in other words, all the feoffees were given equal possession of the fief, an arrangement described as hantgemal. All were given the same rights over their inheritance; they managed a common budget and, where appropriate, had certain officers and judges in common.

The so-called hantgemal agreement was particularly important for laying down the social privileges and estate rights of the noble families involved. A joint inheritance or Ganerbschaft ensured that all family members had this special status and prevented their social status being lowered.