The Simple Words of Catechism (Lithuanian: Katekizmo paprasti odiai) by Martynas Mavydas is the first printed book in the Lithuanian language. It was printed on 8 January 1547 by Hans Weinreich in Knigsberg. The 79-page book followed the teachings of Martin Luther but reflects both religious and secular needs. The book included the first Lithuanian-language poem, primer with alphabet, basic catechism, and 11 religious hymns with sheet music. The book was written in the Samogitian dialect and printed in Gothic (schwabacher) font; Latin dedication and preface are printed in Latin font (antiqua).

Lithuanian (Lithuanian: lietuvių kalba) is a Baltic language belonging to the Balto-Slavic branch of the Indo-European language family. It is the official language of Lithuania and one of the official languages of the European Union. There are about 2.8 million native Lithuanian speakers in Lithuania and about 200,000 speakers elsewhere.

Lithuanian is closely related to the neighbouring Latvian language. It is written in a Latin script. It is said to be the most conservative of the existing Indo-European languages, retaining features of the Proto-Indo-European language that had disappeared through development from other descendant languages.