The story is set in Middle-earth sixty years before the main events of The Lord of the Rings and portions of the film are adapted from the appendices to Tolkien's The Return of the King.

[7] An Unexpected Journey tells the tale of Bilbo Baggins (Martin Freeman), who is convinced by the wizard Gandalf (Ian McKellen) to accompany thirteen Dwarves, led by Thorin Oakenshield (Richard Armitage), on a quest to reclaim the Lonely Mountain from the dragon Smaug.

The ensemble cast also includes Ken Stott, Cate Blanchett, Ian Holm, Christopher Lee, Hugo Weaving, James Nesbitt, Elijah Wood, and Andy Serkis.

The film received numerous accolades; at the 85th Academy Awards, it was nominated for Best Production Design, Best Makeup and Hairstyling, and Best Visual Effects.

Approaching his 111th birthday, the Hobbit Bilbo Baggins begins writing the story of his adventure 60 years earlier for his nephew, Frodo.

Long before Bilbo's involvement, the Dwarf king Thrór brought an era of prosperity for his kin under the Lonely Mountain until the arrival of the dragon Smaug.

In the Shire, 51-year-old Bilbo is tricked by the wizard Gandalf the Grey into hosting a dinner for Thorin and his company of Dwarves: Balin, Dwalin, Fíli, Kíli, Dori, Nori, Ori, Óin, Glóin, Bifur, Bofur, and Bombur.

The wizard Radagast the Brown finds Gandalf and the company, and recounts an encounter at Dol Guldur with the Necromancer, a sorcerer who has been corrupting Greenwood with dark magic.

There, Lord Elrond discloses a hidden indication of a secret door on the company's map of the Lonely Mountain, which will be visible only on Durin's Day.

Cameos in the film include director Peter Jackson and editor Jabez Olssen as Erebor Dwarf refugees running from the dragon Smaug in the opening prologue; picture double Hayden J. Weal as a dwarf carrying gems during Thranduil's visit in Erebor; James Nesbitt's then-wife Sonia Forbes-Adam as Belladonna Took, Bilbo's mother; Nesbitt's daughters Peggy and Mary as children of Dale; Luke Evans as Girion; and production designer Dan Hennah as the Old Took, Belladonna's father.

[19] Del Toro left the project in May 2010, after about two years of working with Jackson and his production team, due to delays caused in part by financial problems at Metro-Goldwyn-Mayer.

[24] Jackson had said that del Toro's sudden exit created problems as he felt he had a very little preparation time remaining before shooting had to begin, with unfinished scripts and without storyboards, which increased the difficulty to direct it.

"[43] Jen Chaney of The Washington Post stated, "Visually and tonally, this preview for [An Unexpected Journey] looks like a perfect match for the Frodo Baggins tales that released in 2001, 2002 and 2003.

"[42] Jackson, Freeman, McKellen, Armitage, Serkis, Wood, and co-screenwriter Philippa Boyens appeared at the 2012 San Diego Comic-Con promoting the film and screening 12 minutes of footage.

[44] On 8 October 2012, Wellington Mayor Celia Wade-Brown announced that for the week of the premiere of The Hobbit: An Unexpected Journey, the capital of New Zealand would be renamed the "Middle of Middle-earth".

[49][50][51] Prince Charles had visited Peter Jackson, the Wētā Workshop and met members of the cast a week before the New Zealand premiere.

[52][53] Around 100,000 people lined the red carpet on Courtenay Place for the film's premiere, and the entire event was broadcast live on TV in New Zealand, as well as streaming over the internet.

[70] By the end of its first weekend it grossed $84.62 million, finishing in first place and setting a then December opening-weekend record (previously held by I Am Legend).

The site's consensus reads "Peter Jackson's return to Middle-earth is an earnest, visually resplendent trip, but the film's deliberate pace robs the material of some of its majesty."

Trolls, orcs, wolves and mountainous monsters made of remarkably pliable stone bring out the best in Jackson and his Rings co-screenwriters Fran Walsh and Philippa Boyens.

He thought the film was "so stuffed with extraneous faff and flummery that it often barely feels like Tolkien at all – more a dire, fan-written internet tribute.

"[85] Time Out magazine's Keith Uhlich called the film "a mesmerizing study in excess, Peter Jackson and company's long-awaited prequel to the Lord of the Rings saga is bursting with surplus characters, wall-to-wall special effects, unapologetically drawn-out story tangents and double the frame rate (48 over 24) of the average movie.

"[86] The Guardian magazine's Peter Bradshaw commented on use of high frame rate technology and length of the film, writing "After 170 minutes, I felt that I had had enough of a pretty good thing.

"[87] Richard Lawson from The Atlantic Wire commented on the film's "video game"-like visual effects, saying "this is a dismally unattractive movie, featuring too many shots that I'm sure were lovely at some point but are now ruined and chintzified by the terrible technology monster.

"[89] Ed Gonzalez of Slant Magazine awarded the film three stars out of four and called it "The first of an arguably gratuitous three-part cine-extravaganza.

"[90] Todd McCarthy of The Hollywood Reporter said that "Jackson and his colleagues have created a purist's delight… [And leads to] an undeniably exciting, action-packed climax."

[92] Dan Jolin of Empire gave the film four out of five stars and thought "The Hobbit plays younger and lighter than Fellowship and its follow-ups, but does right by the faithful and has a strength in Martin Freeman's Bilbo that may yet see this trilogy measure up to the last one" and he stated that "There is treasure here".

An Unexpected Journey also earned five nominations at the 18th Empire Awards, winning in two categories, Best Actor for Martin Freeman and Best Science Fiction/Fantasy Film.