Capax imperii nisi imperasset is a Latin phrase written by Tacitus in Chapter 1.49 of his Histories.

Upon the death of Galba, Tacitus discusses Galba's life and character and ends Chapter 49 with this sentence: Maior privato visus dum privatus fuit, et omnium consensu capax imperii nisi imperasset ("He seemed too great to be a citizen so long as he was a citizen and all would have agreed that he was worthy to the imperial office, if he had never held it").^[1]

It has been said that the phrase is used by Tacitus to sum up Galba's character, as one who seemed to hold all the values of a good leader but failed when he became leader.^[2] In modern times, the phrase has been used to describe leaders who have failed to live up to their expectations.^[3] Jeremy Paxman has quoted the phrase to describe Boris Johnson becoming prime minister,^[4] and it has also been used to describe Gordon Brown.^[5]

• List of Latin phrases
• Peter Principle