A fleet of 14 trains provided by French industrial giant Alstom to the German state Lower Saxony has replaced diesel locomotives on the 100 kilometres (60 miles) of track connecting the cities of Cuxhaven, Bremerhaven, Bremervoerde and Buxtehude near Hamburg.
"We are very proud to put this technology into operation together with our strong partners as a world premiere," Alstom CEO Henri Poupart-Lafarge said in a statement.
Hydrogen trains have become a promising way to decarbonise the rail sector and replace climate-warming diesel, which still powers 20 percent of journeys in Germany.
Billed as a "zero emission" mode of transport, the trains mix hydrogen on board with oxygen present in the ambient air, thanks to a fuel cell installed in the roof. This produces the electricity needed to pull the train.
Regional rail operator LNVG said the fleet, which cost 93 million euros (dollars), would prevent 4,400 tonnes of CO2 being released into the atmosphere each year.