The mammalian oocyte does not develop in isolation. Throughout its protracted life history, from primordial germ cell specification to ovulation, the female gamete develops within a dynamic immune microenvironment that both supports and monitors its development. This review synthesizes current knowledge on the immunobiological mechanisms governing oocyte quality, with particular emphasis on how immune cells, cytokines, and inflammatory signaling pathways shape oocyte developmental competence across the reproductive lifespan. We examine the prenatal origins of ovarian immune colonization, the functional roles of tissue-resident macrophages, dendritic cells, and T lymphocytes in follicular dynamics, and the molecular pathways through which immune signals influence meiotic fidelity and mitochondrial function. The concept of the ovarian immune microenvironment as a critical determinant of oocyte quality is developed, integrating evidence from physiological ovarian aging and pathological conditions including primary premature ovarian insufficiency (POI). We further explore how immune checkpoint pathways, inflammasome activation, and senescence-associated secretory phenotype (SASP) converge to mediate age-related oocyte decline in preclinical models, with correlative human evidence supporting these observations. In preclinical models, these pathways have been associated with impaired oocyte quality through distinct mechanisms: spindle disruption and chromosome misalignment (TNF-α, IL-6), mitochondrial dysfunction and ATP depletion (NLRP3 activation, ROS), lipid peroxidation-induced membrane damage (ferroptosis), and impaired developmental competence manifesting as reduced fertilization and blastocyst formation rates (chronic inflammation); human evidence remains largely correlative. Emerging immunomodulatory strategies for fertility preservation are critically evaluated. This review conceptualizes oocyte quality as a property of immune-endocrine-stromal interactions and proposes microenvironment-aware models of female reproductive competence, while explicitly grading the strength of the underlying evidence.