Augustinus Rotundus (Polish: Augustyn Rotundus, Lithuanian: Augustinas Rotundas, 1520–1582) was a Christian and Renaissance humanist, erudite, jurist, political writer, first historian and apologist of Lithuania. Rotundus was vogt of Vilnius, general secretary to the Grand Duke and King Sigismund Augustus and elder of Stakliškės. After his nobilitation to the szlachta, Rotundus adopted surname Mieleski, or Milewski.
Rotundus was born in Wieluń around year 1520. His surname is supposed to be "Mieleski", although some researchers suggest that it was adopted later. Rotundus is translated nickname, probably inherited from his father – Mikołaj (English: Nickolas) "Okrągły" (Latin: Rotundus), who was a rich furrier in the city of Wieluń.
Rotundus studied in University of Wittenberg and Lubrański Academy in Poznań, where he was suspected of writing a nasty lampoon about Poznań catholic chapter. Undoubtedly Rotundus was a passionate catholic after graduation and supported Hereditary monarchy and Execution movement.
He arrived in Vilnius, capital of the Grand Duchy of Lithuania on August 20, 1551. He was invited by Grand Duke of Lithuania Sigismund Augustus as a legal advisor, and one who knew both Grand Duchy and Crown's law. Assigned as vogt of Vilnius in 1552 (most probably suggested by city inhabitants), he became loyal citizen of Lithuania, and wrote several works on Lithuania's history and political polemic works defending Lithuania's rights. In 1558 he was appointed as elder of Stakliškės.