The Polonus Polish Philatelic Society is the oldest and largest society in the USA dedicated to the study and promotion of Polish philately.

Founded in February 1939 by Chester Mikucki, Polonus grew from a "local Chicago club" into one of the largest and most active specialized philatelic societies in the world, and now boasts an international membership. The word "Polonus" was reportedly created by Kopernik (Copernicus), the famous astronomer, who, when attending the university at Padua, Italy registered as "Kopernik; nationality, Polonus."

Throughout its history, Polonus has been active in promoting all facets of Polish philately. Its membership has written a large number of articles on all aspects of Polish philately. The society was instrumental in promoting the issuance of several US commemorative stamps including (1) Poland Overrun Countries issue, Scott # 909; (2) Paderewski Champion of Liberty issue, Scott # 1159-1160; (3) Poland Millennium issue, Scott # 1313; and (4) Copernicus issue, Scott # 1488.

The Polonus Bulletin, official publication of the society has been published since 1942. The Bulletin has contained hundreds of articles on both generalized and specialized facts of Polish philately. Many of these articles have been published in the international philatelic press.