Mainz has excellent train connections from Frankfurt am Main, just 35 minutes by S-Bahn (S8 or S9) on the frequent commuter rail service. The Frankfurt airport is reachable directly by S-Bahn without changing. From Wiesbaden, just across the Rhine, the journey takes about 15 minutes.
The main train station (Hauptbahnhof) is a 10-minute walk west of the old town. Long-distance ICE and IC trains connect Mainz with Cologne (about 90 minutes), Mannheim (30 minutes), and other major German cities. Drivers find parking difficult in the old town — the city is better approached by train.