Founders' cults throughout Southeast Asia are based on the contract between the original founder or founders of a settlement and the spirit owner or owners of territory cleared for human use. The establishment and enactment of these cults reflect relationships with founding ancestors and with neighboring polities. Founders' cults are implicated in defining both ethnic identity and interethnic relations. Changes in the cults involve the representation of identity through the enactment of traditional local custom in response to European colonialism, world religions, and the penetration of global capitalism. Here, through comparative inquiry and ethnographic case studies, ten anthropologists examine founders' cults in mainland and insular Southeast Asia.