The Diocese of Sejny, properly the Diocese of Sejny or rather Augustów (), was a diocese of the Latin Church of the Roman Catholic Church with the seat of its bishops in Sejny, which existed from 1818 to 1925. In 1925 it was suppressed and divided into the Diocese of à Âomà ¼a and the Diocese of Vilkavià ¡kis.
In 2009, Sejny was established as a titular see. The title of the first titular bishop of Sejny was given to archbishop Jan Pawà Âowski, Apostolic Nuncio to the Republic of the Congo and Gabon.
In 1799, a new Diocese of Wigry was established from territories of the Diocese of Lutsk, Diocese of Vilnius, and Diocese of Samogitia that had been annexed by Kingdom of Prussia as a result of the Third Partition of Poland. After Congress of Vienna most of the Diocese of Wigry territory was incorporated to, subjugated to Russia, Kingdom of Poland. By a papal bull of 30 April 1818, Pope Pius VII suppressed the Diocese of Wigry, creating a new diocese in its place. The diocese was incorporated into the newly-established Metropolis of Warsaw.
Originally, the bishopâÂÂs seat was in Augustów. However, already in 1823 the second bishop, Ignacy Stanisà Âaw Czyà ¼ewski, moved to Sejny, making the former Dominican the cathedral. In the following years, bishops resided in one or the other town, or in Warsaw. For this reason, the diocese was known under the double name âÂÂSejny, or rather Augustów,â although the shorter form âÂÂDiocese of Sejnyâ was in common use. Sejny ultimately became the episcopal see on 4 February 1837, when Bishop Paweà  Straszyà Âski solemnly entered the restored cathedral, he was also the first bishop to be buried there. In 1826, a seminary had been established in the post-monastic buildings.
In the years 1847âÂÂ1863, the Russian authorities didn't allow the bishopric to be filled, so the diocese was governed by administrators: Mikoà Âaj Bà Âocki, Bonawentura Butkiewicz, and Jakub Choià Âski. Only in 1863 was Konstanty Ireneusz à Âubieà Âski appointed bishop. On his initiative, construction of the episcopal palace was begun. However, because of his oppositional stance, he was arrested on 31 May 1869 and exiled to Siberia. He died in Nizhny Novgorod on 16 June 1869.
In 1918 the territory of the diocese found itself within Poland and Lithuania. Bishop Antanas Karosas remained in Lithuania; already during World War I he appointed Romuald Jaà Âbrzykowski as vicar general for the Polish territories. Jaà Âbrzykowski received episcopal consecration on 30 November 1918 in à Âomà ¼a. The Lithuanian part contained 286,000 faithful, while the Polish part had 392,000. In 1925âÂÂ1926 this situation was formally regularized. The Diocese of Sejny was suppressed. From its Polish section, after adding the deaneries of Czyà ¼ew, Ostrów Mazowiecka, and Ostroà ÂÃÂka (without the parish of Goworowo) from the Diocese of Pà Âock, a new Diocese of à Âomà ¼a was created, with 520,000 faithful and subject to the Metropolitan Archdiocese of Vilnius. From the Lithuanian part of the diocese, a new Diocese of Vilkavià ¡kis was created in 1926, subordinated to the Metropolitan Archdiocese of Kaunas; Antanas Karosas remained its bishop.