ABSTRACT Saline coastal ecosystems arise from interacting marine and terrestrial processes, in which soil salinization, sea-level fluctuations, and anthropogenic disturbances jointly constrain ecological stability. Halophytes — salt-tolerant vascular plants comprising approximately one percent of global flora — play a significant functional role in these environments, frequently dominating vegetation associations in semi-desert, coastal plain, and saline meadow systems. This review synthesizes current knowledge of halophyte functional ecology in saline coastal systems, with particular reference to the Caspian coastline of Azerbaijan. The Azerbaijani Caspian coast spans approximately 800 km and encompasses six phytogeographical regions, supporting a documented flora of approximately 1,054 vascular plant species. Halophytes meeting the ≥200 mM NaCl life-cycle criterion (Flowers & Colmer, 2008) constitute an estimated 8–9% of this flora. Based on published global literature and regional floristic surveys, five ecosystem stability functions are described: topsoil ion redistribution, sediment modification, succession facilitation, biodiversity structuring, and carbon storage. The physiological mechanisms associated with these functions — including vacuolar ion compartmentalization, salt gland secretion, osmotic adjustment, and antioxidant defence — are well documented in the global literature but remain unmeasured in Caspian coastal populations. No original experimental data are presented. All quantitative values are derived from published sources, and their applicability to the non-tidal, petroleum-affected, and irrigation-salinized Caspian system is explicitly discussed. The review provides a structured synthesis of existing knowledge, distinguishing between globally established mechanisms and region-specific observations, and outlines directions for future empirical research.