Poland is not very diverse when it comes to nationalities. With
Poles being majority [over 99%], other nationalities include:
Germans [ca. 190k], Belarusians [ca. 50k] and Ukrainians [ca. 30k].
Other include Tatars, Lithuanians, Roma, Lemkas, Russians, Slovaks,
Czechs and Armenians. Those are accounted citizens. There is
unaccounted number of Asians, most prominently Vietnamese [those
numbers can go up to 50 or 70k].
Recognized ethnic minorities (but not nationalities) include
Kashubians (current Polish Prime Minister is Kashubian) and
Silesians.