Short bowel syndrome (SBS) arises from extensive intestinal resection and is characterized by a progressive process of intestinal adaptation, where the residual bowel undergoes both structural and functional modifications to restore nutrient absorption and reduce dependence on parenteral support. This chapter provides a comprehensive overview of the mechanisms underpinning intestinal adaptation, emphasizing the influence of the anatomical site of resection on absorptive capacity, adaptation potential, and clinical outcomes. Differences in adaptation between the jejunum and ileum, the role of the colon, epithelial regeneration, transporter expression, hormonal regulation, and microbiota shifts are discussed.