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.

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

Together with Shvarn, Vaišvilkas attacked Poland in 1265 to avenge the Yotvingians' defeat a year prior.

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