File Photo: A Patriot missile launcher. AP
"Today, our beautiful Ukrainian sky becomes more secure because Patriot air defence systems have arrived in Ukraine," Defence Minister Oleksiy Reznikov said on Twitter.
He added that the United States, Germany and the Netherlands had "kept their word".
Washington late last year said it would provide Ukraine with its Patriot air defence system as Russia pounded Ukraine's energy infrastructure from the air.
Ukrainian President Volodymyr Zelensky has said the system will "significantly" strengthen Ukraine's defence against Russian strikes.
Russian President Vladimir Putin dismissed the announcement at the time, saying Russia will find an "antidote".
Germany announced in January that it was following the United States in sending one of the advanced missile defence batteries to Ukraine.
The Netherlands said it would supply parts of a Patriot air defence system to Ukraine, specifically two launchers and missiles.
Separately, the Ukrainian army said Wednesday that France's light AMX-10 RC armoured fighting vehicles were "already in service".