Rimantas Jasas (1929-2002) was a Lithuanian historian. He was born in Šiauliai, where he lived until 1936 when his family moved to Utena. At the end of the Second World War, his father emigrated to the USA, and his mother was sent to Siberia in 1948. Rimantas Jasas concealed these facts when he became a member of the Komsomol. He even started to work as a laboratory assistant in the Department of Marxism-Leninism at Vilnius Pedagogical Institute, although he was soon accused of withholding information and sacked. In 1952, Jasas started studying history at Vilnius University. He graduated from the university in 1957, and started working at the Lithuanian Institute of History. In 1968, he moved to the Library of the Lithuanian Academy of Sciences, where he worked till the end of his life.

While Jasas did not undertake formal doctoral studies (he deliberately refused), he was considered a leading specialist in the history of the Grand Duchy of Lithuania, knowing the archival sources very well. He prepared and translated the Bychovets Chronicle (published in 1971). Even today, this publication is a standard example of a perfect work on historical sources. Nevertheless, while working at the library, Jasas was overloaded with technical work that impeded his research work. The reason for this negative situation was the lack of political trust in him by the regime.