Quercetin, a polyphenolic flavonoid abundant in fruits and vegetables, exhibits strong antioxidant, anti-inflammatory, cardioprotective, anticancer, and neuroprotective effects. However, its therapeutic use is hindered by poor solubility, low absorption, rapid metabolism, and limited bioavailability. Conventional enhancement methods such as micronisation and cyclodextrin complexation offer only partial improvement. Phytosome technology provides an effective solution by forming molecular complexes between quercetin and phospholipids like phosphatidylcholine. This amphiphilic structure enhances lipophilicity, membrane permeability, and systemic retention, resulting in nanosized particles (100–300 nm), high entrapment efficiency (>80%), and up to fourfold higher bioavailability. Preclinical and early clinical studies confirm improved antioxidant, hepatoprotective, neuroprotective, and anti-inflammatory efficacy, with good safety and tolerance. Remaining challenges include large-scale production, stability, and cost. Future progress depends on green synthesis, polymer-coated or co-phytosome systems, and harmonised global regulations to ensure quality and safety.