Hildesheim is on the main rail line between Hannover and Göttingen. Trains from Hannover run every 30 minutes and the journey takes about 25 minutes. From Hannover Hauptbahnhof there are direct connections to most major German cities, and Hannover airport is a further 20 minutes from the city.
From Göttingen the train journey takes about 45 minutes. Hildesheim is also directly reachable from Paderborn and Braunschweig without changing trains. The Hildesheim Hauptbahnhof is about 10 minutes' walk from the market square and cathedral.
By car, Hildesheim lies just off the A7 motorway (the main north-south route through western Germany), making it easy to include as a stop on a longer journey.