The Hammer of Thor is an American young-adult fantasy novel based on Norse mythology written by Rick Riordan.

It was published on October 4, 2016 as a hardcover, audiobook, and ebook, and is the second book in the Magnus Chase and the Gods of Asgard series.

The novel takes place six weeks after the events of the preceding story, The Sword of Summer, and chronicles Magnus Chase's quest to retrieve the missing hammer of Thor and prevent Loki's rise to power.

The Hammer of Thor received positive reviews from critics, who praised its inclusion of diverse characters such as the genderfluid character Alex Fierro, Muslim Samirah al-Abbas, and deaf-mute Hearthstone, but also noted its trite and repetitive plot that did not help readers progress through the series' overall story arc.

Magnus returns to Hotel Valhalla to rest and prepare, where he meets Alex Fierro, Sam's newest einherji recruit and a transgender/genderfluid child of Loki.

Magnus, Sam, and their friends Blitzen and Hearthstone travel to the Provincetown barrow but discover the Skofnung Sword instead of Thor's hammer.

Magnus and Hearthstone track down a dwarf named Andvari and force him to give them his treasure, which they use to repay Hearth's debt.

To retrieve the hammer and stop the giants' invasion of Midgard, the quest group must go through with the wedding and deliver the Skofnung Sword to Loki.

Magnus's hallmates and a group of gods arrive and defeat the giants, but Loki escapes, and Randolph is killed by the spirits of the sword.

Magnus contacts his cousin Annabeth to ask for help from her boyfriend Percy Jackson, son of Poseidon.

[11][12] In a radio interview conducted in Iowa City, Riordan discussed his character choices and the kinds of themes he wanted to present in the series, including increased awareness of Muslim-American issues, and his inspiration and writing method.

He also highlighted the differences between his approach to Norse mythology and that of other popular media series such as the Marvel Cinematic Universe, which he described as "fast and loose".

[25] To date, editions have also been released in Spanish, French, Chinese, German, Italian, Polish, Portuguese, Dutch, Swedish, Finnish, Czech, Danish, Bulgarian, Turkish, and Hebrew.

Maggie Reagan of Booklist wrote, "Riordan combines Norse mythology with a number of social issues: [gender fluidity, disability, and race and religion]", calling the book "a surefire hit".

[30] Todd Kleiboer of The East Texan, the student newspaper of Texas A&M University-Commerce, claimed that although Riordan does well to include such diverse characters as the Muslim Samirah and genderfluid Alex, the author runs the risk of making his readers believe such characters are representative of their "group" by portraying only one example of each "type" of person.

He continues, "Young adult readers may have no contact with the Muslim or transgender population outside of literature, and most will take Samirah or Alex as representatives.

[37][38] When asked about his decision to include Alex, Riordan said, "There’s lots of kinds of kids out there, and my feeling is that all of them deserve to be able to see themselves in stories".

[39] An official announcement by the American Library Association said, "Alex is a hero and represents the expansive possibilities of gender for future generations".