Nineteenth-century art historian John Addington Symonds coined the term hæmatomania (blood madness) for the extremely bloodthirsty behaviour of a number of disturbed rulers like Ibrahim II of Ifriqiya (850–902) and Ezzelino da Romano (1194–1259). According to Symonds, this mental pathology was linked to melancholy and caused by an excess of black bile. I explore the historical credibility of this theory of ‘wild melancholy’, a type of melancholia that crucially deviates from the lethargic main type. I conclude that in its pure form Symonds’ black bile theory of hæmatomania was never a broadly supported perspective, but can be traced back to the nosology of the ninth-century physician Ishaq ibn Imran, who practised at the Aghlabid court, to which the sadistic Ibrahim II belonged.