The Golden Bull of Rimini was a Golden Bull issued by Emperor Frederick II, at his court in Rimini in March 1226 to confirm the Teutonic Knights' possessions in Prussia. It was the first of three similar documents, followed by the Treaty of Kruschwitz (Kruschwitz) in 1230, and the papal Golden Bull of Rieti in 1234.
The Piast duke Konrad I of Masovia had waged several Prussian Crusades and particularly in 1222/23 had tried to conquer Chełmno Land (Culmer Land) east of the Vistula River from the pagan Old Prussians. Backed by his Polish cousins Leszek I the White and Henry I the Bearded, he initially was successful, but had to face a Prussian counterstrike and now feared for his Duchy of Masovia, which suffered under continuous Prussian attacks. In 1224 the duke began negotiations with the Teutonic Knights to strengthen his forces and to stabilize the situation.
Between 1211 and 1225, the Teutonic Order, led by Grand Master Herman of Salza, was present in the Burzenland region of Transylvania. Similar to Konrad of Masovia's request, the Knights had been called in by King Andrew II of Hungary to settle, stabilize and protect the eastern Hungarian frontier against the Cuman people. Yet, they were expelled after trying to establish an autonomous state on Hungarian territory, subordinate only to the authority of Pope Honorius III. This time von Salza would wait to set out for Prussia, until the Order's claimed possessions were confirmed directly by the Holy Roman Emperor.
The Knights were to be equipped by Duke Konrad I of Masovia in exchange for their support to stabilize his Masovian land:"...our trusty Brother Herman, the worthy Master of the Sacred House of the Hospital of St. Mary of the Germans in Jerusalem
[i.e., the Teutonic Order
] has explained ... that our devoted Konrad
(Chünradus), Duke of Masovia and of Kujawy
(Cuiaviae), has promised and undertaken to provide for him and to his brethren from that land, which is called the Chelmło Land
(terra quae vocatur Culmen), and in that other land, that is to say, between his borderland
(marchiam) and the territories of the Prussians
(confinia Prutenorum), that they may thus indeed take up the task and readily embark upon the invasion and obtaining of the land of Prussia
(terram Prusciae) for the honor and glory of the true God.
"We [that is, Frederick himself] therefore... especially because the land itself is held under the sole rule of the Empire
(sub monarchia imperii), trusting also in the judgment
(prudentia) of the same Master, because he is a man mighty both in deed and word and through his own and his brethren’s perseverance is mightily undertaking and manfully carrying out the conquest of that land... even though many, vainly besought with numerous exertions in this business, gave up
(defecerunt) just when they seemed about to set forth, grant the land of Prussia to the same Master along with the forces of his order and with all those who think to invade [it]
This Imperial authorisation was signed by a large number of princes, such as the Archbishops of Magdeburg, Ravenna, Tyre, Palermo and Reggio, the Bishops of Bologna, Rimini, Cesena, Mantua and Tortosa, the Dukes of Saxony and Spoleto, and the Margrave of Montferrat.
Duke Konrad actually had no intention of ceding Chełmno Land and therefore established his own military Order of Dobrzyń (Fratres Militiae Christi) in 1228, whom he vested with Dobrzyń Land. The few brethren. however, were not able to secure the borders of Masovia against the Prussian raids and Konrad faced the threat of losing his whole duchy.
On 16 June 1230, the Treaty of Kruszwica was supposedly signed, according to which Duke Konrad ceded the lands of Chełmno, as well as all other conquests made in Prussia, to the Teutonic Knights under Grand Master Hermann von Salza and the Order of Dobrzyń. The text is only known by later references, as the original document is not preserved. According to the historian Max Perlbach (1848-1921), the Knights forged it to create a legal basis for their secular possessions.
In 1234, Pope Gregory IX issued the Golden Bull of Rieti, Pietati proximum, confirming the prior deals, stating that the Prussian lands of the Order were subject only to the Pope, not a fief of any other secular or ecclesiastical power. The Roman Curia had already made a promise confirming this; nevertheless, von Salza had insisted on its being put in writing.
The bull was again confirmed by Pope Alexander IV in 1257.