Fidei commissum (Latin ‘to leave in trust’) is an institution of inheritance and property law, according to which the assets of a family, usually land property, were to be preserved in perpetuity through a foundation and only one family member alone, the fidei commissum owner, held the usufructuary right. This is to be distinguished from the private property of a family member (the sovereign), the casket, which was subject to his free disposal during his lifetime and after his death.
The family fideicommissariat is similar to fiefs, ancestral estates and family foundations.
