Intraductal papillary neoplasm of the bile duct (IPNB), formally recognized in the 2010 and updated in the 2019 WHO classifications, represents a pre-invasive biliary neoplasm with high malignant potential that ultimately may progress to an invasive carcinoma. It is characterized by exophytic growth within dilated bile ducts lined by papillary/villous neoplastic epithelium. IPNBs are histologically categorized into intestinal, gastric, pancreatobiliary, and oncocytic types, with a newer subclassification—Type 1 and Type 2—based on location, mucin production, and invasiveness, offering better prognostic correlation. Correct diagnosis and mapping rely on a combination of CT/MRI/MRCP and cholangioscopy. Surgical resection remains the primary treatment, while lymph node status and resection margin are key prognosticators. Type 1 IPNBs generally show superior long-term outcomes compared to Type 2. Recent genomic analyses have revealed subtype-specific mutations, paving the way for molecular risk stratification and future targeted therapies.