Martynas Mažvydas (1510 – 21 May 1563) was the author and the editor of the first printed book in the Lithuanian language.
Variants of his name include Martinus Masvidius, Martinus Maszwidas, M. Mossuids Waytkūnas, Mastwidas, Mažvydas, Mosvidius, Maswidsche, and Mossvid Vaitkuna.
Mažvydas was a prolific 16th century Lithuanian author, who is associated with the beginnings of Lithuanian literature. He was of Samogitian origin, born near Žemaičių Naumiestis (now in Šilutė district municipality) in the Grand Duchy of Lithuania; his parents were said to be indigent townspeople. Mažvydas spent his youth in Vilnius, where he worked together with other pioneering Lithuanian authors from the Grand Duchy of Lithuania, such as Abraomas Kulvietis, Jurgis Zablockis, and possibly Stanislovas Rapolionis. Later Mažvydas would publish some of their works.
In Roman Catholic Lithuania Mažvydas was persecuted for his Protestant leanings, which motivated him to accept an invitation from Duke Albrecht of Prussia to come to Königsberg. He entered Albertina University in 1546; in 1548 he graduated from the university with a bachelor's degree. The fact that Mažvydas graduated in one-and-a-half years suggests that he had studied elsewhere before – possibly in Kraków, or at the school established by Kulvietis in Vilnius. It has also been suggested that he was teaching at Albertina University.
To spread the new Protestant faith in Prussia, Duke Albrecht commissioned the translation and publication of Lutheran texts in Old Prussian and Lithuanian. In the year 1547, while still a student in Königsberg, Mažvydas and his collaborators compiled and published the first printed Lithuanian book Catechismusa Prasty Szadei ("The Simple Words of Catechism")- which was based on the Polish version of Martin Luther's "Kleiner Katechismus" -, thus launching literature and book printing in Lithuanian. This book shows characteristics of the Samogitian dialect of Lithuanian, with clearly visible Aukštaitian traits. It was printed at about the same time as the first books in neighbouring nations' languages: Polish in 1513 or 1514, Belarusian in 1522, Estonian in 1535, and Latvian in 1585.