Background <p>Gallbladder stone (GBS) is a frequent complication in type 2 diabetes mellitus (T2DM), yet effective tools for baseline risk estimation remain lacking. This study aimed to develop and validate a clinically practical nomogram for individualized GBS risk assessment in T2DM patients using multicenter real-world data.</p> Methods <p>In this retrospective multicenter study, 1,762 T2DM patients with an intact gallbladder who underwent abdominal ultrasonography at two tertiary hospitals were included. The primary center provided a training set (<i>n</i> = 914) and internal validation set (<i>n</i> = 392), and the second center provided an external validation cohort (<i>n</i> = 456). Logistic regression was used to build a nomogram for ultrasound-detected GBS at the index visit, and its performance was evaluated by ROC analysis, calibration, and decision curve analysis (DCA).</p> Results <p>Six factors—age ≥ 60 years, longer diabetes duration, elevated HbA1c, FPG, TG, and presence of diabetic peripheral neuropathy (DPN)—were independently associated with GBS. The nomogram showed good discrimination in the training (AUC = 0.82), internal (0.81), and external (0.82) validation cohorts. Calibration curves demonstrated consistency between predicted and actual risk, and DCA confirmed clinical usefulness.</p> Conclusions <p>This nomogram offers a simple, non-invasive tool for estimating baseline GBS risk in T2DM patients, and may assist in risk stratification, targeted monitoring, and preventive counseling in outpatient diabetes care.</p> Clinical trial number <p>Not applicable.</p>