Codex Athous Dionysiou, designated by Ω or 045 (in the Gregory-Aland numbering), ε 61 (von Soden), is a Greek uncial manuscript of the New Testament.

[3] It contains lists of the κεφαλαια (tables of contents) before each Gospel, the τιτλοι at the top, the Ammonian Sections (in Mark 234 Sections), references to the Eusebian Canons, lectionary equipment in the margins, illustrations, liturgical books Synaxarion and Menologion, subscriptions at the end of each Gospel, and numbers of στιχοι (stichoi).

The Greek text of this codex is a representative of the Byzantine text-type, with some Alexandrian readings.

According to Hermann von Soden it is one of the three oldest manuscripts that present the earliest variety of the Byzantine text-type (after S and V).

[6] In John 1:29 it lacks ο Ιωαννης along with manuscripts Sinaiticus, Alexandrinus, Vaticanus, Cyprius, Campianus, Petropolitanus Purpureus, Vaticanus 354, Nanianus, Macedoniensis, Sangallensis, Koridethi, Petropolitanus, Athous Lavrensis, 047, 0141, 8, 9, 565, 1192;[7] In John 5:25 it has "Son of Man" instead of "Son of God".