Elymus repens (L.) Gould, commonly known as couch grass, is mainly distributed as a medicinal herb of great ethnopharmacological importance. This review presented for the first time the significance of nomenclature clarity, current insights on distribution, traditional use, phytochemistry and their biological activities. The bioactive compound composition of E. repens displayed a variety of compounds including carbohydrates, phenolic acids, flavonoids, benzoxazinoids and volatile compounds, all of which contributed to its medicinal properties. The biological potential of this plant underlines diuretic, antiurolithiatic, anti-inflammatory, antioxidant and also antidiabetic qualities with molecular insights showing synergistic interactions across many compound classes. The current reported data notably confirmed its potential in lowering renal calculi and alleviating associated symptoms; however, the findings remain limited. E. repens’ medicinal potential is further confirmed by its historical application as an herbal tea and aqueous preparation, which clearly indicates its favorable safety profile. Along with this, from many encouraging results, there exist considerable deficiencies in standardization, clinical validation and also mechanistic clarification. This review highlights the necessity for careful studies to determine the therapeutic efficiency, enhance formulation and promote E. repens as a scientifically therapeutic agent.