The Waltzian structural realism emerged as the quintessential neorealism after 1986. Throughout the 1990s, many realists sought to transcend, if not entirely abandon, structural realism by devising new theories. Many of them (some retrospectively) were grouped under the category of defensive realism. This chapter attempts to make sense of defensive realism, both as a variety of unique theories and as a disarrayed whole. To this end, the initial six sections of the chapter discuss six different theorists/theories commonly associated with defensive realism: (1) Robert Jervis’ offense-defense-balance theory; (2) Kenneth Waltz’s balance-of-power theory; (3) Stephen Walt’s theory of alliance formation; (4) Jack Snyder’s theory of over-expansion; (5) Stephen Van Evera’s “misperceptive fine-grained structural Realism”; (6) Charles Glaser’s “contingent realism.” The seventh section elucidates multiple senses in which defensive realism is commonly defined. It concludes that defensive realism consists of a variety of theories that are “defensive” and “realist” in different, often ambiguous, ways. In short, defensive realism is an indeterminate subcategory of the disarrayed tradition of realism.