The Great Karnak Inscription of Merneptah's 5th regnal year, the longest surviving continuous monumental text from Egypt, describes the combined Libyan and Sea People invasion of Egypt c.1208 BCE. This new study, the first complete commentary on this long but unfortunately damaged text, begins with a translation of the text, accompanied by detailed notes. The study considers specific military aspects of the inscription alongside its religious background. A grammatical analysis of the Great Karnak Inscription also sheds new light on the grammar of Ramesside monumental texts.