Frequent relocations and disruptions to social support systems are just one of many factors inherent to military life that underscore the importance of cultivating a sense of belonging. Other challenges, such as adapting to new cultures and environments, managing family dynamics, and navigating the uncertainty of deployment schedules, further complicate establishing roots and a sense of community. A robust body of research has explored important links between belonging and various physical and mental health outcomes for military service members, with research focused on military spouses remaining notably sparse. Utilizing Social Constructivist Grounded Theory, this qualitative study addressed this significant gap through in-depth interviews conducted with a purposive sample of 40 military spouses, including those from marginalized and underrepresented groups. Findings shed light on how military spouses construct a sense of belonging against the backdrop of ever-changing social environments. The impact of interactions across ecological layers on belonging is explored, introducing a new theoretical framework that distinguishes between enduring (trait) and situational (state) belonging. This framework examines the intersectionalities of rank dynamics, racial disparities, and gender stereotypes and emphasizes the fluidity of belonging. Implications for military communities, social work theory, policy, and practice with military families are discussed.