Hamburg's main fan zone will be on the Heiligengeistfeld grounds, next to St Pauli's stadium (as shown on the map below).

With space for 10,000 people, it will be showing all Euro 2024 games on numerous big screens.

The best to get there from elsewhere in the city is either on foot (if you're not too far away) or by public transport. The St. Pauli underground station (served by the U3) is located very close to the Heiligengeistfeld and thus provides a very easy and convenient way to reach it. The Reeperbahn 'S-Bahn' suburban train station (served by the S1 and S3) is also only a short walk away, as is the Landungsbrücken S-Bahn station (served by the S1, S3 and U3).

More info here: Hamburg Euro 2024 fan zone