Vaišvilkas or Vaišelga (also spelled Vaišvila, Vojszalak, Vojšalk, Vaišalgas;[1] died 18 April 1267) was Grand Duke of Lithuania from 1264 until his death in 1267.

[6] Nothing is known about the youth of Vaišvilkas as he entered historical sources only in 1254 when he made a treaty, in the name of his father King Mindaugas, with Daniel of Halych-Volhynia.

After Vaišvilkas was baptized in a Greek Orthodox rite, he was drawn to religious life so much that he transferred his title and lands to Roman Danylovich, son of Daniel of Halych.

[9] Then they waged a war against Nalšia and Deltuva, two main centers of opposition to Mindaugas and Vaišvilkas.

[7] Lithuanian support of the Great Prussian Uprising ceased, and the orders made advances against Semigallians and Curonians uninterrupted.

[9] When in 1267 he decided to go back to monastic life, Vaišvilkas transferred the title of Grand Duke to Shvarn.