Lublin Mayor Krzysztof Żuk announced the news via social media, Polish state news agency PAP reported.
He said Mykoła Miałkowski was killed while fighting the Russian invasion of Ukraine.
Żuk extended condolences to the official's family and said that Miałkowski died while "defending his homeland and fighting for freedom."
Miałkowski, 28, had overseen academic cooperation projects at Lublin City Hall and was also a student at the Catholic University of Lublin (KUL), the PAP news agency reported.
In August, Miałkowski told regional broadcaster Radio Lublin that he had joined his country's territorial army after Russia's February 2022 invasion.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Tuesday is day 650 of Russia’s war on Ukraine.
Source: PAP, Polish Radio Lublin