Mistborn is a series of epic fantasy novels by the American author Brandon Sanderson and published by Tor Books. The first trilogy, commonly referred to as "Era One", was published between 2006 and 2008 and consists of The Final Empire, The Well of Ascension, and The Hero of Ages. A second series, officially titled Wax and Wayne and informally known as "Era Two", was released between 2011 and 2022, and consists of the tetralogy The Alloy of Law, Shadows of Self, The Bands of Mourning, and The Lost Metal. A novella was released in 2016, Mistborn: Secret History, relating to a hidden side of the events of Era One. Sanderson intends to write a third and fourth Mistborn series, with the third series' official title being Ghostbloods.

The first Mistborn trilogy chronicles the efforts of a secret group of Allomancers who attempt to overthrow a dystopian empire and establish themselves in a world covered by ash. The first trilogy was a commercial success. This success pushed Sanderson to further develop his fictional universe, the Cosmere, which also includes The Stormlight Archive. Set about 300 years after the ending of the first trilogy, the second series is about the exploits of a character forced to move into the big city, and starts investigating kidnappings and robberies. The third series will be set in the early computer age with 1980s/1990s technology. The fourth series is planned to be a space-opera.

Sanderson's first idea for Mistborn came while reading the Harry Potter series: He thought it would be interesting to set a story in a world where the "dark lord" triumphed and the "prophesied hero" failed. His second idea, originally unrelated, was to tell a heist story in a fantasy setting, an idea inspired by the Ocean's series. The idea for the titular mist came while he was driving through mist in Idaho, which he combined with his memories of having once seen Washington National Cathedral lit from the inside. He originally developed feruchemy and allomancy for separate stories before deciding to bring them together in one story.

Sanderson began work on Mistborn: The Final Empire while trying to get his earlier novel Elantris published. After writing two early iterations of Mistborn, he shifted his focus to his Stormlight Archive series. However, Sanderson chose to delay its publication in favor of completing the Mistborn series, which he thought would serve as a better follow-up to Elantris.

The original trilogy published by Sanderson was the first in what he used to call a "trilogy of trilogies." Sanderson planned to publish multiple trilogies all set on the fictional planet Scadrial but in different eras: the second trilogy was to be set in an urban setting, featuring modern technology, and the third trilogy was to be a science fiction series, set in the far future. However, this structure changed with the release of The Alloy of Law, which began a new series set between the first trilogy and the planned second trilogy. After some confusion, Sanderson decided to refer to the overall series in terms of four eras, with Era One being the first trilogy, Era Two being the four books starting with The Alloy of Law, and Eras Three and Four being the other planned trilogies.

The series primarily takes place in a region on the planet of Scadrial. The events of Era One primarily take place in Classical Scadrial, specifically within the Final Empire, while Era Two and beyond take place in Post-Catacendre Scadrial.

The history of Scadrial started with Preservation and Ruin, two opposing gods (Known in-universe as Shards of Adonalsium, and therefore fragments of the power of creation). Preservation's nature made him want to preserve things in their current state indefinitely, whereas Ruin was destruction without malice, intent on reducing everything to a state comparable to the Heat death of the universe. While each possessed considerable power alone, they could neither create nor destroy completely. As forces of opposite intent, they could nevertheless join forces to make something (satisfying Preservation) which could also be destroyed (Ruin's desire). As a result, they created Scadrial. To prove to Ruin that he could destroy Scadrial when the time came, Preservation created humans, modeled on humanity they had already encountered in the Cosmere, infusing a part of himself in their creation, weakening himself. The deal was that Ruin would be allowed to destroy the world one day, but Preservation was determined to prevent that from happening. Preservation used his own mind to create a prison, the Well of Ascension, and trapped Ruin's mind inside, preventing him from destroying Scadrial.

Nevertheless, despite their mutual incapacitation, Ruin and Preservation remained aware, and possessed sufficient powers to influence events directly. Humans eventually discovered that the Metals of Scadrial could be ingested and burnt by some of them (Allomancy), granting them special powers such as enhanced strength, hearing, speed and various other abilities. Unknown to them, the Metals were fragments of Preservation and Ruin's bodies. As a result, even from his prison, Ruin could directly influence people pierced by Hemalurgic spikes created by stealing a portion of a soul using a metal spike. Aware that Ruin could influence them and that his prison had a flaw that could allow it to be opened every millennium, Preservation gave humanity the Terris Prophecies, a series of predictions of what would happen when the Well of Ascension would start calling out to the Metalborn of the world.