Codex 0308 (in the Gregory-Aland numbering), is one of the recently registered New Testament Greek uncial manuscripts. It consists of only a fragment of a single parchment leaf of a fourth-century codex, containing portions of the eleventh chapter of the Book of Revelation.
The surviving texts of Revelation are verses 11:15-16 and 11:17-18; they are in fragmentary condition. Uncial 0308 measures with the surviving leaf having 11 lines out of an original 14 (see reconstruction below). The text was written one column to a page, though line lengths were irregular. The letters à(epsilon) and à(theta) have an extended middle line, and they are similar to those from Codex Washingtonianus. These characters appear influenced by the shape of Coptic letters. The nomina sacra attested in this uncial fragment are <span style="text-decoration: overline">ÃÂã</span> (Kurios, Lord) and <span style="text-decoration: overline">çáã</span>) (Christos, Christ). The number "twenty four" is also written using an abbreviation â <span style="text-decoration: overline">ÃÂÃÂ</span>. All the abbreviations are marked with the superscript bar.
Although the text of the codex is too brief to determine its textual character, it concurs with both Codex Sinaiticus and with ðÂÂÂ<sup>47</sup> (Papyrus 47), with one exception. In Rev 11:16 it has the textual variant , agreeing with Codex Alexandrinus, Uncial 051 and <sup>A</sup> against úñø÷ýÃÂñùâÂÂðÂÂÂ<sup>47</sup> and Codex EphraemiâÂÂalso ÿù úñø÷ýÃÂñùâÂÂSinaiticus and <sup>K</sup>. In Rev 11:17 it has , a variant supported by: ðÂÂÂ<sup>47</sup>, ÃÂ, C and 2344. In Re 11:18 it has textual variant "" (like: Sinaiticus and ðÂÂÂ<sup>47</sup>), Textus Receptus and NA27 have: "". It differs two times with NA27 (úñù used 2 times more). The text of the codex was published by W. E. H. Cockle in 1999.
It is cataloged among the Oxyrhynchus Papyri as P. Oxy. 4500, and is now part of the Sackler Library collection in Oxford.