Cicero's speech delivered in the mid 50s BC in defense of Gaius Rabirius Postumus was the last of a series of trials which followed the restoration of the Egyptian king, Ptolemy XII Auletes, to his throne. This book provides a new translation the speech and the first commentary in English of a work which is a major source for Roman and Egyptian history at the time of the late Republic. The extensive introduction furnishes a comprehensive review of the events surrounding the trial as well as a significant reappraisal of the career of Rabirius Postumus who is shown to be a major actor on the Roman political stage. The detailed commentary discusses historical and legal points and also includes a number of important textual emendations.