Herodotus' portraits of the four Persian kings in the Histories present the reader with four very distinct personalities. This offers an opportunity to compare them with each other as individuals, rather than as linked parts of an overall Herodotean pattern (such as the rise and fall of empires), and to use detailed differences between them at the micro-level as the basis for an analysis of each one's own unique style of leadership. My analysis takes as its starting point the classification of three of the kings allegedly made by the Persians themselves (see 3.89.3), focusing on all four kings' styles as presented within the contexts of Persian imperialism; advice and advisers; and three specific modes of behaviour (violence, uncertainty and fear). Each king is shown consistently to exhibit his own style of leadership - Cyrus as piealphaτήρ, Cambyses as deltaεsigmapieότης, Darius as kappaάpieηGammaος, and Xerxes as a consultative leader. My analysis uncovers Herodotus' awareness of many aspects of the problem of leadership in a monarchical system (such as the tension between offering sound advice and delivering mere flattery), as well as his non-judgmental approach to each individual king's style. I go on to deploy a number of modern leadership theories to assess the extent to which they can be fruitfully applied to the Persian kings' styles of leadership, concluding that the breadth of Herodotus' accounts of the leadership styles exhibited by the Persian kings draws attention to the shortcomings of such modern leadership theories in the inadequate assessment of the extent to which the majority of leaders perform, or fail to do so; and further that such modern leadership theories underline the exceptional quality of Cyrus' leadership and his uniqueness among the Persian kings, while at the same time suggesting the immense difficulty of sustaining a monarchical system in the absence of such quality leadership. Overall the analysis demonstrates how in the Histories Herodotus with subtlety and insight presents the reader, in a detailed and analytical way, with an engaged portrayal of ideas about leadership and its practice.