Ukonvasara, or Ukonkirves, is the symbol and magical weapon of the Finnish thunder god Ukko, similar to Thor's Mjölnir. Ukonvasara means 'hammer of Ukko'; similarly, Ukonkirves means 'axe of Ukko'. It was said that Ukko created lightning with Ukonvasara.

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages) This whole article needs additional citations for verification. (December 2006) You can help expand this article with text translated from the corresponding article in Finnish. (February 2017) Click [show] for important translation instructions. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing Finnish Wikipedia article at [[:fi:Ukon kirves]]; see its history for attribution. You should also add the template {{Translated|fi|Ukon kirves}} to the talk page. For more guidance, see Wikipedia:Translation.

Ukko's hammer was probably originally a boat-shaped stone axe. When stone tools were abandoned with the advent of metalworking, the origins of stone weapons became a mystery. Stone axes, so-called thunderstones (ukonvaaja in Finnish), were found in the ground, especially after drenching rains washed away dirt. They were believed to be weapons of Ukko, stone heads of the striking lightning. Shamans collected and held stone-axes because they were believed to hold the power to both heal and damage.^{[citation needed]}

Followers of modern Finnish paganism sometimes carry hammer or axe pendants around their necks, much like Christians sometimes wear crosses.^{[citation needed]}

According to Asko Parpola, the Proto-West-Uralic *vaśara, originally referred to the axe or mace of the Sejma-Turbino warriors, but later, under Nordic influence, gained the meaning "hammer" from Thor's hammer. The Proto-West-Uralic *vaśara, is an early loanword from the Proto-Indo-Aryan *vaj’ra- but not from Proto-Iranian, because its palatalized sibilant is not consistent with the depalatalization which occurred in Proto-Iranian. The related Sanskrit vajra- and its Avestan cognate vazra- are possibly derived from the Proto-Indo-European root *weg'- which means "to be(come) powerful", state Parpola and Carpelan.^[1][2]

Unto Salo [fi] believes that Ilmari, another Finnic sky god, is the origin of Ukko, but that as Ukko Ilmari experienced very significant, although far from total, influence from the Indo-European sky god especially in the form of Thor.^[3][4] Others believe that Ukko's original name was Baltic Perkūnas.^[5]

Perkūnas is pictured as middle-aged, armed with an axe and arrows, riding a two-wheeled chariot harnessed with goats, like Thor.^[6] The name Thor descends from the Proto-Germanic theonym *Þun(a)raz ('Thunder').^[7] According to scholar Peter Jackson, those theonyms may have originally emerged as the result of the fossilization of an original epithet (or epiclesis) of the Proto-Indo-European thunder-god *Perk^wunos.^[8] from which Perkunas also descended from ^[9]

Indra is described as using the vajra to kill sinners and ignorant persons.^[10] Indra's mythology parallels Perun, Perkūnas, Taranis, and Thor, suggesting a common origin in Proto-Indo-European mythology.^[11][12][13]

• Mjölnir
• Vajra