Abi T. Ngunga explores the theme of messianism in the entire corpus of the Old Greek of Isaiah (LXX-Isaiah). This is done through the lens of an intertextual hermeneutic employed by the Isaiah translator as a mode of reading this text.Its introductory chapter looks at the need in scholarship to investigate the topic of messianism in the Greek Bible in general, and in the whole of the LXX-Isaiah in particular. After dealing with a few issues related to the LXX-Isaiah as a translation, Ngunga also surveys thoroughly the topic of intertextuality from its inception to its use in biblical studies including LXX research. Particular attention is given to its application in research done, to date, on the Greek text of Isaiah.Chapter two re-examines a few arguments pertinent to the scholarly opinion that messianic hopes were not prominent among the Alexandrian Jews in comparison to their co-religionists in Palestine. It also explores the relationships between the non-Jewish citizens of the Ptolemaic kingdom and the Alexandrian Jews, with the aim to ascertain the legitimacy of investigating the theme of messianism in a piece of Jewish literature such as the LXX-Isaiah authored in the Hellenistic period. Chapter three analyses in-depth nine selected messianic passages within the LXX-Isaiah (7:10-17; 9:1-7(8:23-9:6); 11:1-10; 16:1-5; 19:16-25; 31:9-32:8; 42:1-4; 52:13-53:12; and 61:1-3a). The study concludes by highlighting the detected particular messianic imprints left on the LXX-Isaiah. Given the results, the study dismisses any doubt concerning the contention that there is a dynamic messianic thought running through the whole of the Greek Isaiah. It also sheds some light on the understanding of some of the messianic beliefs later echoed in early Christianity.