Viking warriors wore horned or winged helmets.
There is no evidence, archaeological or otherwise, that Viking warriors wore any type of horns or wings on their helmets. What we do have is one single piece of evidence, the ninth century Oseberg tapestry, suggesting a rare ceremonial use (the relevant figure on the tapestry may even be that of a god, rather than representative of real Vikings) and plenty of evidence for plain conical/domed helmets made mainly of leather.
Horns, Wings and Wagner
I’m sure we’ve all seen them, pictures of large, hairy men with horns sticking proudly out of their helmets as they rush to rape and pillage. It’s so common it must be true surely? Well, no. Years of excavations, coupled with studies of images, have yielded no evidence for the common use of horned or winged Viking warrior helmets. So where has the idea come from? Roman and Greek writers referred to northerners who wore horns, wings and antlers, amongst other things, on their helmets. Like much contemporary writing about anyone non-Greek or Roman there appears to have already been a distortion here, with archaeology suggesting that while this horned headgear did exist, it was largely for ceremonial purposes and had largely faded out by the time of the Vikings, often considered to have started in the late eight century. This was unknown to the writers and artists of the early modern era, who began referencing the ancient authors, making misinformed jumps and depicting Viking warriors, en masse, with horns. This image grew in popularity until it was taken on by other forms of art and passed into common knowledge. The temporary mis-identification of a Bronze Age carving in Sweden with a horned helmet as Viking didn’t help matters, although this was corrected in 1874.
Perhaps the greatest step on the way to the ubiquity of the horn was in the late nineteenth century, when costume designers for Wagner’s Nibelungenlied created horned helmets because, as Roberta Frank puts it “humanist scholarship, misunderstood archaeological finds, heraldic origin fantasies and the Great God Wish...had worked their magic” (Frank, 'The Invention...', 2000). Within just a few decades the headwear had become synonymous with Vikings, enough to become shorthand for them in advertising.
Roberta Frank quotation cited from Frank, ‘The Invention of the Viking Horned Helmet’, International Scandinavian and Medieval Studies in Memory of Gerd Wolfgang Weber, 2000.