«MOTU PROPRIO». — Generally indicates a document relating to a grant made by a sovereign on his own initiative, whether real or fictitious, taking its name from the first words with which the text usually begins. This formula is adopted either to justify the extraordinary nature of the grant or to produce certain legal effects in favour of the beneficiary.
In the Papal Chancery it constitutes a particular type of document since the 15th century and continues to the present day: written on paper, it bears at the top the name of the Pope in the manner of briefs and begins with the words «M. p.»; the subscription, in the Pope’s own hand, was expressed by the formula «Placet m. p.», followed by the initial of his baptismal name (today the formula «Placet» is omitted and the name is that of his reign); it lacks a seal and other formalities.