After Thor's face was scarred by Hela, he grew a beard to cover his injuries.
Thor's Beard was created by Walt Simonson.
Thor sported his beard for quite a while until he eventually shaved it off at the insistence of the Warrior's Three. Thor's Beard has resurfaced several times since.
Major Beard Arcs
Thor's Beard made it's public debut to the people of Midgard during the Mutant Massacre when Thor's Beard accompanied the Thunder God to the sewers to help X-Factor battle against the Marauders.
Traitor in our Midst
The Avengers are betrayed by one of their own and Thor's Beard ain't too happy about it (neither is Thor).
In the classic Avengers story, the Masters of Evil take over Avengers Mansion and have all but defeated the team... until Thor's Beard arrives and helps Ant-Man and Wasp turn the tide of the battle.
Contest of Death
When the Avengers fought against Death, Thor's Beard was one of the many who died only to be resurrected by stories end.
Assault on Olympus
When the Avengers were the target of the Gods of Olympus due to injuries Hercules had received while a member, Thor's Beard played a vital part in the infamous "Battle of the Beards" between him and Zeus.
The Morgan Conquest
Thor's Beard returned in the opening saga of the Avengers in the post-Heroes Return world.
Lord of Asgard
When Odin perished, Thor assumed rule over Asgard and throughout his tenure as Lord, Thor's Beard returned to his face possibly to look more wise or because his consort Amora the Enchantress liked the way it tickled her face.
Thor locked horns with his Avengers comrade Tony Stark in Standoff, battling over who had the greater beard. Captain America got confused and joined in despite not having a beard.
Heart of the Infinite
Thor's Beard achieved an audience of Eternity and Infinity when cosmic-powered Pharaoh Akhenaten threatened the order of the Universe.
In the Ultimate Universe, Thor's Beard is present as a member of the Ultimates.
In Other Media
Marvel Ultimate Alliance (2005)
Thor's default costume in the Marvel Ultimate Alliance game is based upon his Ultimate design and as such sports Thor's Beard. One of Thor's unlockable costumes is based on his Lord of Asgard look and also sports Thor's Beard.
Thor's Beard appears in Marvel Studios' Thor, portrayed by Chris Hemsworth's Facial Hair.
Hemsworth's Facial Hair reprises the role of Thor's Beard in the blockbuster Avengers movie.
Thor: The Dark World (2013)
Thor's Beard is set to return (again played by Hemsworth) in the sequel to Thor.