Martin Wilibald Schrettinger (June 17, 1772 in Neumarkt in der Oberpfalz – April 12, 1851 in Munich) was a German priest and librarian.
In 1793 he joined the Benedictine monastery in Weißenohe, where he was ordained in 1795. In 1800 he became the monastery's librarian. In 1802 shortly before the closing of the monastery he went to Munich where he worked for the Royal Library (now the Bavarian State Library). He assumed the titles of curator (Kustos) in 1806 and in 1823 Under-librarian. In 1839, while still retaining his position as librarian, he was installed as a Canon at Munich's St. Kajetan.
Schrettinger is regarded as the founder of modern library science and was the first person to use the term. He created a catalog of all the library's holdings divided into subjects and sub-subjects. He cross-referenced these through an alphabetic catalog of authors and a catalog of locations within a library where books were shelved. In 1819 he began a classified catalog (Realkatalog), which itself is sometimes consulted by modern librarians and remains unfinished.