Vaišvilkas or Vaišelga (… – December 9, 1268) was the third grand duke of Lithuania, serving from 1264 to 1267, when he abdicated in favor of his brother-in-law Švarnas. He was perhaps the eldest son of Mindaugas, the first and only ruler of the kingdom of Lithuania.
Nothing is known about Vaišvilkas” young age, as historical sources speak of him only from 1254, when he entered into a treaty acting in the place of his father, King Mindaugas, with Danilo of Galicia-Volinia. In the treaty, Galicia-Volinia ceded Black Ruthenia and its main center Navahrudak to Lithuania. To consolidate the treaty, Danilo”s son Švarnas married Vaišvilkas” sister. The latter was appointed duke of some of these lands. After Vaišvilkas was baptized according to the Greek Orthodox rite, he was so attracted to the religious universe that he transferred his title and possessions to Roman Danilovič, son of Danilo of Galicia. He founded a monastery traditionally identified with Lavrashev Monastery on the bank of the Neman River and became a monk. He set out on a pilgrimage to Mount Athos in Greece. He did not reach his destination because of wars in the Balkans, managing to stop only in Bulgaria and then return to Navahrudak, now Belarus.
In 1264, he escaped the plot hatched by Treniota and Daumantas against his father and two of his brothers. When the murder took place, Vaišvilkas was in the monastery of Pinsk: he fled there as soon as he heard the news, as he was still among the papal legitimate heirs. Treniota was murdered in 1264 by former servants of Mindaugas. Vaišvilkas allied himself with his brother-in-law Švarnas of Galicia-Volinia and managed to take control of and Black Ruthenia and some of the former territories of the Duchy of Lithuania lost in the wars against some dissident local groups. Later, they waged war against Nalšia and Deltuva, two settlements that had strenuously opposed Mindaugas in the past. Daumantas, duke of Nalšia, was forced to flee to Pskov. Suksė (or Suxe), another influential duke of Nalšia, fled to Livonia. Having eliminated usurper and conspirators, Vaišvilkas became grand duke of Lithuania. As a Christian, he tried to maintain peaceful relations with the Teutonic knights and the Livonian order. He entered into a peace treaty with Livonia regarding trade on the Daugava River. Lithuanian support for the great Prussian revolt ceased and warriors were instead diverted northward to fight against Semigalli and Curi. Still flanked by Švarnas, Vaišvilkas attacked Poland in 1265 to avenge the devastation caused by the Iotvingians in 1264.
At the end of 1267 he chose to re-embrace monastic life: as soon as he began the following year, Vaišvilkas ceded the title of Grand Duke to his brother-in-law. A year later he died at the hands of Švarnas”s brother, Lev I of Galicia, who resented that power had not been shared between him and his brother. He was buried at the Church of the Assumption in Volodymyr-Volyns”kyj.
The mystery of this Grand Duke”s real Lithuanian name has puzzled linguists and historians. The various reconstructions have led to two credible variants: Vaišvilkas, based on Woyszwiłk and Vaišelga, based on Vojšalk. The name Vaišvilkas was first reconstructed by Lithuanian linguist Kazimieras Būga. In fact, the first part of the compound noun, vaiš-, does not generate problems and is present in very similar forms. It is the second part, -vilka, or “wolf,” that is extremely rare or almost nonexistent in Lithuanian names. For this very reason the scholar felt that the original name could have been Vaišvilas.
Gaining most popularity in historical writings was the variant Vaišelga
Alongside these two hypotheses, a third, admittedly minority hypothesis can be identified: some researchers even suggest that the Grand Duke had two names, one of which was Vaišvilas.