Codex Ambrosianus is an extremely important folio-sized Syriac (Eastern Aramaic) manuscript of the entire Aramaic Peshitta Old Testament. It is formally known as MS B. 21 Inf; 7a1 in the Leiden Peshitta Institute Edition of the Aramaic Old Testament.
Codex Ambrosianus is currently located in the Ambrosian Library in Milan, Italy, hence its name. It dates to the sixth or seventh century A.D., and is written in Estrangela script. It was acquired around 1006 or 1007 A.D. by the Monastery of the God-Bearer, also known as Dier Al-Suryani (Arabic for The Monastery of the Syrians) situated in the Wadi Nitrun in the desert of Scetis south of Alexandria, Egypt.
Codex Ambrosianus includes all the books of the Old Testament (the Tanakh, or Hebrew Bible). Like a number of other Aramaic Old Testament manuscripts, it also includes several of the Apocryphal books which are outside the Western Canon. These include the Wisdom of Solomon, Letters of Jeremiah and of Baruch, Bel and the Dragon, Susanna, Judith, Ben Sirach, 1 Maccabees, 2 Maccabees, 3 Maccabees, 4 Maccabees, 2 Baruch with the Letter of Baruch, 2 Esdras, and Book VI of Josephus' The Jewish War. The books in Codex Ambrosianus appear to be arranged in historical, rather than traditional canonical, order.
Codex Ambrosianus is the only Syriac manuscript to contain the Apocalypse of Baruch and IV Ezra in full.
The manuscript was discovered by Antonio Ceriani in 1866 and published in 1876-1883. It was moved to Milan in the 17th century. The manuscript was used as the base text for the critical edition of the Aramaic Peshitta Old Testament (Peshitta Tanakh) being produced by the Leiden Peshitta Institute. An electronic version of the canonical books of Codex Ambrosianus, based on that of the Leiden Peshitta Institute, can be examined at the Comprehensive Aramaic Lexicon. A morphologically tagged edition of this electronic version is available in Accordance Bible software.
Codex Ambrosianus is carefully written in the Estrangela script, and is arranged in three columns per side. There are only five missing folios which are noted in the Latin preface. The manuscript contains 330 folios.
A photolithographic Facsimile Edition of Codex Ambrosianus was published in Milan by A. M. Ceriani, called Translatio Syro Pescitto Veteris Testamenti Ex Codice Ambrosianus, or "The Syriac Peshitta Old Testament Translation from Codex Ambrosianus" (Milan: Angeli della Croce, 1876-1881).