Background/Objectives: Rebamipide is a gastroprotective agent with poor aqueous solubility and rapid gastrointestinal clearance, leading to reduced therapeutic efficiency. This study aimed to enhance the solubility, mucoadhesion, and sustained oral delivery of Rebamipide through the development of a deep eutectic mixture (DEM)-based bioadhesive controlled-release granule formulation. Methods: In silico hydrogen-bonding interactions between Rebamipide, malonic acid, and urea were analyzed using CCDC tools. A thermodynamically stable DEM (1:3:1) was prepared and incorporated into bioadhesive granules using chitosan and HPMC. Physicochemical characterization was conducted using FTIR, DSC, TGA, and PXRD. Solubility, in vitro dissolution, ex vivo mucoadhesion (sheep gastric mucosa), and in vivo gastric retention (BaSO₄-loaded granules in rats) were evaluated. Results: The optimized DEM significantly enhanced Rebamipide solubility (10.08 mg/mL vs. 0.045 mg/mL). Solid-state analyses confirmed hydrogen-bond formation and reduced crystallinity. DEM granules exhibited sustained drug release over 24 h (99.7 ± 0.8%) with improved dissolution efficiency compared to the marketed tablet (Mucosta®, 100 mg; T₅₀%: 5.03 h vs. 0.82 h). Kinetic modeling indicated non-Fickian anomalous transport (n = 0.47). The bioadhesive force of DEM granules (0.29 ± 0.02 N) was significantly higher than that of the pure drug and physical mixture. In vivo radiographic studies confirmed prolonged gastric retention. Conclusions: The DEM-based bioadhesive granule system effectively improves solubility, dissolution rate, mucoadhesion, and gastric retention of Rebamipide. This approach represents a promising platform for once-daily gastroretentive oral delivery, pending further pharmacokinetic evaluation.