The first shipment of Leopard 2 tanks from Germany has been sent to Ukraine, the German defence ministry says.
Eighteen cutting-edge main battle tanks were delivered after Ukrainian crews were trained to use them.
Defence Minister Boris Pistorius said he was sure the tanks could "make a decisive contribution" on the frontlines of the war.
Challenger 2 tanks from the UK have also arrived, according to reports from Ukraine.
Ukraine has been calling for more modern vehicles and weapon systems for months to help fight Russia's invasion.
The Ukrainian government is yet to comment on the arrival of the Leopard 2s, but they have confirmed the arrival of the first UK-made Challenger 2 tanks.
Around 2,000 Leopard 2s, widely regarded as being among the best main battle tanks produced by Nato countries, are in use by European countries.
Germany agreed to supply the tanks to Ukraine in January, after being initially reluctant to do so - or even to permit other countries from sending their own.
Under German law, Berlin must approve Leopard 2s being re-exported by any country.