Mark Duncan de Cérisantis (died 1648) was a Scots-descended French and Swiss diplomat, before becoming secretary to Henry II, Duke of Guise.
Shortly afterwards he left the Swedish service, renounced his Protestantism, and went to Rome, where in 1647 he met Henry II, Duke of Guise, then meditating his attempt to wrest the kingdom of Sicily from Spain, whom he accompanied to Naples in the capacity of secretary.
He is said also to have been secretly employed by the French king to furnish intelligence of the duke's designs and movements.
The genuineness of the work is, however, now beyond dispute, and it must be observed that the duke, while imputing to Cérisantis excessive vainglory, gives him credit for skill and intrepidity in the field.
[1] Cérisantis was esteemed one of the most elegant Latinists of his age, and published several poems, of which Carmen Gratulatorium in nuptias Car.