Peppermint (Mentha × piperita L.), a hybrid of spearmint and watermint, has been widely utilized in traditional medicine for its aromatic, cooling, and analgesic properties. The principal bioactive constituent, menthol, is primarily responsible for peppermint’s muscle relaxant and pain-relieving effects. Recent pharmacological investigations have elucidated that menthol acts as a selective agonist of transient receptor potential melastatin 8 (TRPM8) channels, producing a cooling sensation that modulates nociceptive transmission. Additionally, menthol influences voltage-gated sodium channels, calcium influx, and neurotransmitter release, thereby contributing to peripheral and central analgesic effects. Beyond sensory modulation, menthol exhibits smooth and skeletal muscle relaxation by interfering with calcium mobilization within muscle fibers and inhibiting contractile responses mediated by muscarinic and histaminergic pathways. Experimental studies demonstrate that topical peppermint oil or menthol formulations significantly reduce muscle tension, improve blood flow, and alleviate symptoms of myalgia, tension-type headaches, and exercise-induced muscle soreness. Preclinical data from animal models show dose-dependent attenuation of inflammatory mediators, oxidative stress markers, and neuronal hyperexcitability following menthol administration. Clinical evidence supports the topical application of peppermint oil (2–10% concentration) for localized muscle pain, with favorable safety and tolerability profiles. Its rapid onset of action, minimal systemic absorption, and low incidence of adverse effects make it an attractive alternative or adjunct to conventional muscle relaxants and analgesics. However, variability in oil composition, formulation type, dosage, and application frequency influences therapeutic outcomes. Standardization of peppermint oil products and rigorous, large-scale randomized controlled trials are necessary to establish optimal therapeutic protocols. Furthermore, nanocarrier-based delivery systems and synergistic polyherbal formulations represent promising avenues for enhancing bioavailability, targeted delivery, and sustained release of menthol for muscle relaxation. This review consolidates mechanistic insights, experimental and clinical evidence, and formulation strategies related to peppermint’s role in muscle relaxation. By bridging traditional usage with modern pharmacological understanding, it highlights peppermint and menthol as potential safe, effective, and accessible interventions for managing muscle pain and related disorders.