Cicero’s speech delivered in the mid 50s BC in defence 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 had been secured through the services of a Roman army which had acted on the promise of a huge illegal bribe. Rabirius Postumus, a leading financier, had travelled to Egypt to collect the promised money acting on behalf of himself and other creditors of the king, including Caesar and Pompey. On his return political opponents placed him, amongst others, on trial. 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.