Deutsche Bahn and numerous transport associations in Germany started selling 9-euro monthly tickets on Monday.
In the early hours of the morning alone, around 50,000 tickets were sold via Deutsche Bahn's digital channels, a company spokesman said.
In the morning, the site was repeatedly overloaded due to high demand.
The 9-euro ticket was also available on Monday via the DB Navigator train app.
Anyone who booked a trip in regional transport via the mobile app came across the offer during the process.
With the special tickets, passengers can travel throughout Germany in the valid month for 9 euros on local public transport.
The monthly tickets can be booked for June, July and August.
The federal government wants to relieve consumers in view of the high inflation with the offer and also make the switch to public transport more attractive.
Citizens should switch to public transport
Last Friday, the Federal Council cleared the way for 9-euro monthly tickets in June, July and August, which are valid everywhere in local and regional transport.
They are part of the federal government's relief package because of the high energy costs and are intended to encourage citizens to switch from cars to public transport.