The band were a favourite with those following the competition as viewers became invested in their journey to the finals, held today, even as their country battled Russia's invasion.
The folk-rap group scored 631 points at the final in Turin, Italy, amid a set of 25 songs from bands representing countries around the world.
The UK's Sam Ryder won second place, with 466 points, in the highest position for a UK artist in 20 years. Third and fourth place went to Spain and Sweden respectively.
The competition is scored half from points from audience votes and half from votes cast by a jury of five music industry professionals.
Kalush Orchestra drew an emphatic audience response throughout the competition, and paused at the end of their final performance to also ask for help for Ukrainian forces in besieged Mariupol.
This year fan feeling online called for fewer ballads and more bangers among the 25 song entries.
Performers, representing their country, also public cast votes for each other, adding to the dramatic tension. However, competition organisers have announced there was irregular jury voting from six countries in the second semi-final.
The European Broadcast Union said it calculated a "substitute aggregated result for each country concerned for both the second semi-final and the grand final".
And said it: "takes any suspected attempts to manipulate the voting at the Eurovision Song Contest extremely seriously."
Urkainian president Volodymyr Zelensky has congratulated the band on their win for Ukraine.
"Our courage impresses the world, our music conquers Europe," he wrote on Telegram.
"We will do our best to one day host the participants and guests of Eurovision in Ukrainian Mariupol. Free, peaceful, rebuilt," he added.