Codex Koridethi, also named Codex Coridethianus, designated by siglum Θ or 038, ε050, is a Greek uncial manuscript of the New Testament, written on parchment. Using the study of comparative writing styles (palaeography), it has been assigned to the 9th century CE. The manuscript has several gaps.

In the textual criticism of the New Testament, the Byzantine text-type is one of the main text types. It is the form found in the largest number of surviving manuscripts of the Greek New Testament. The New Testament text of the Eastern Orthodox Church, the Patriarchal Text, as well as those utilized in the lectionaries, are based on this text-type. Similarly, the Aramaic Peshitta which often conforms to the Byzantine text is used as the standard version in the Syriac tradition, including the Syriac Orthodox Church and the Chaldean church. Whilst varying in at least 1,830 places, it also underlies the Textus Receptus Greek text used for most Reformation-era (Protestant) translations of the New Testament into vernacular languages. Modern translations mainly use eclectic editions that conform more often to the Alexandrian text-type, which is viewed as the most accurate text-type by most scholars, although some modern translations that use the Byzantine text-type have been created.