Towarzysz pancerny ("mailed companion"; plural: towarzysze pancerni, or pancerni) was a medium-cavalryman in 16th to 18th century Poland, named for his chainmailarmor ("pancerz"). These units were the second-most-important cavalry arm in the Polish army, after the hussars.
Most pancerni were recruited from the middle or lower classes or szlachta (nobility). They were organized into companies, with each company (Polish: chorągiew) consisting of 60 to 200 horsemen.
In the medieval times, during the rule of Mieszko I and Bolesław I Chrobry, pancerni were members of the prince's own force, and they alone in the whole army wore mail armour.
In modern Polish, "pancerni" also means "tank men", as in the title of the book and TV series, Czterej pancerni i pies (Four Tank Men and a Dog). The word "pancerny" is seldom used in that context, however, the common word being "czołgista" (from "czołg", "tank").