The Territorial Imperative: A Personal Inquiry Into the Animal Origins of Property and Nations is a 1966 nonfiction book by American writer Robert Ardrey.

The Territorial Imperative is the second book in Ardrey's Nature of Man Series; it is preceded by African Genesis (1961) and followed by The Social Contract (1970) and The Hunting Hypothesis (1976).

In African Genesis, Ardrey posited that man originated in Africa instead of Asia, that he is driven by inherited instincts to acquire land and defend territory, and that the development of weapons was a fundamental turning point in his evolution.

[5] Montagu would eventually edit another volume in opposition to Ardrey,[6] and the increasingly heated debate stirred popular interest in human origins.

By Carmel Schrire's account, "Ashley Montagu edited two collections of writings aimed at countering the views of both Ardrey and Konrad Lorenz.

Robin Fox, who authored The Imperial Animal (1972) with Lionel Tiger, wrote of the opposition: I was a great friend of Robert Ardrey, and had been known publicly to defend his name and honor from the assault of the anti-Ardreyites, including Ashley Montagu.

[16] Geoffrey Gorer, for example, in his Encounter review of The Territorial Imperative, writes: "Almost without question, Robert Ardrey is today the most influential writer in English dealing with the innate or instinctive attributes of human nature, and the most skilled populariser of the findings of paleo-anthropologists, ethologists, and biological experimenters.

"[14] Commenting upon Ardrey's legacy on the occasion of his death, the South African anthropologist Dr. Phillip Tobias stated, "He has made an incalculable contribution to the science of human evolution.

Thousands of people around the world, especially in the United States, were made aware of the fascination and the importance of studies on man's place in nature [through his writing].

[19][20] The strategic analyst Andrew Marshall and U.S. Secretary of Defense James Schlesinger are known to have discussed The Territorial Imperative in connection to military-strategic thinking.