Elevated allostatic load (AL) has been associated with the risk and poor prognosis of many chronic diseases. The association between AL and inflammatory bowel disease (IBD) is unknown. The aim of this study is to investigate the associations between AL and the risk and prognosis of IBD. We included 326,345 adults and 3767 patients with IBD from the UK Biobank. AL served as the exposure, estimated using the AL biomarker panel, with the primary outcomes including the risk and prognosis of IBD. We used Cox regression models to examine the associations. High AL biomarker panel was associated with a greater risk of IBD (hazard ratio: 1.19, 95% CI: 1.08-1.31), ulcerative colitis (1.17, 95%CI: 1.04-1.32), and Crohn's disease (1.25, 95%CI: 1.05-1.49). Risk of developing IBD increased by 12% in quartile 2, 20% in quartile 3, and 37% in quartile 4 as AL biomarker panel increased. The all-cause mortality risk in IBD compared with quartile 1 rose by 54% for quartile 2, 72% for quartile 3, and 82% for quartile 4, as AL biomarker panel increased. Similar effects were also observed for ulcerative colitis and Crohn's disease. An increase in AL biomarker panel count was associated with an elevated risk of intestinal resection and colorectal cancer in IBD. Increased AL is associated with IBD risk, as well as the risks of intestinal resection, colorectal cancer and mortality.