Diabetes mellitus represents a global health challenge affecting over 500 million individuals worldwide, with insulin remaining the cornerstone of glycemic control for type 1 diabetes and advanced type 2 diabetes. Despite its therapeutic efficacy, subcutaneous insulin administration faces significant limitations including patient non-compliance, injection-associated pain, needle phobia, and failure to replicate physiological insulin secretion patterns. Oral insulin delivery has emerged as a transformative alternative that promises needle-free administration, improved patient adherence, and restoration of hepatoportal insulin gradients mimicking endogenous secretion. However, the gastrointestinal tract presents formidable physiological barriers including harsh gastric acidity, proteolytic enzyme degradation, mucus layer impedance, and limited intestinal epithelial permeability. This comprehensive review examines the pathophysiology of gastrointestinal barriers, advanced pharmaceutical strategies for oral insulin formulation, emerging nanotechnology-based delivery platforms, permeation enhancement mechanisms, targeted intestinal absorption strategies, and clinical translation progress. We critically evaluate encapsulation technologies, pH-responsive polymers, protease inhibitors, mucoadhesive systems, nanoparticle carriers, cell-penetrating peptides, and receptor-mediated transport exploitation. Furthermore, we discuss pharmacokinetic optimization, bioavailability enhancement, safety considerations, regulatory pathways, and future directions toward achieving clinically viable oral insulin therapeutics for transforming diabetes management.