Bishopric of Selonia (Semgallia), 1218–1251

… we decree by the authority entrusted to us that the land called Semgallia shall be joined to the diocese of Riga, so that the Bishop of Riga shall possess Semgallia entirely, with all spiritual and temporal jurisdiction and rights, except one third of the same land, which the brothers of the Teutonic House of Saint Mary currently possess, with tithes and full temporal jurisdiction, and which they have beld up to now. Henceforth, no separate bishop shall be appointed in Semgallia, because that region forms a part of the diocese of Riga, for it is not so vast that it could sustain a separate bishopric even if the whole were converted to the faith…

With this decision, the diocese of Selonia (Semgallia) was liquidated in 1251 by Cardinal Legate Guglielmo, Cardinal Bishop Pietro da Collemezzo and Cardinal Priest John of Toledo. The diocese had only been established 33 years earlier, with great hopes of winning the southern shore of the Daugava for the Crusaders.

However, after the establishment of the diocese, Selonia was no longer the focus of the Crusaders' attention: instead, Mežotne, located in the basin of the Lielupe, became the center of Selonia, though the territory was now more commonly referred to as Semgallia. A cathedral was planned to be built at Mežotne and it was also the seat of the cathedral chapter. By all accounts, it could be assumed that the bishops of Semgallia would become important ecclesiastical princes of Livonia, rulers of a secular and spiritual territory.

In this title we investigate why this did not happen and how this diocese was soon liquidated. We will also examine the two known castles of the bishops of Selonia or Semgallia, Babite and Mežotne.