The "Shake It Off" singer began the awards show with her first televised performance of "Blank Space," featuring a live (yet framed) version of her mansion-set music video, complete with a burning rose, a choking suitor, and dancers dressed as zombie ex-lovers. She also transformed her copper-colored gown into a flirty fringe number.
The musician started off his monologue just after Swift's performance, of which the host joked, "She just sold another 68 million albums!" And since he's called "Pitbull, Mr. 305, Mr. Worldwide — with three names, they should pay me triple!" He also joked that among the audience, he saw "black, white, pink, purple, orange, Asian, Latinos —and guess what? President Obama said, we can all stay!" in reference to his immigration address, and laughed, "ABC found out last year that when I spoke just 3 Spanish words, ratings went up 142 percent, so get ready for three hours of just subtitles!"
Patrick Dempsey awarded the first honor of the night to One Direction. "America feels like a second home to us know, it's been amazing how well we've been received," said Liam Payne alongside his four bandmates.
Introduced by The Fault in Our Stars' lead Ansel Elgort, Charli XCX took the stage to perform "Boom Clap" off of the romantic drama's soundtrack, as well as a bit of "Break the Rules" to the prom-themed set.
Matthew Morrison and Rita Ora introduced a performance of "Rude" by MAGIC! and Wyclef Jean's "Divine Sorrow."
While presenting the award for Favorite Rap/Hip Hop Album, Jamie Foxx took to the stage with his adorable daughter, Annalise.
Iggy Azalea won for The New Classic, and it's "the first award I ever won in my entire life, and it means so much to me that it's best hip hop, because that's what inspired me … to get through my life, to better times," she said alongside T.I.
Introduced by Gavin Degraw and Becky G, the Australian band took the stage for a cover of The Romantics' 1979 track, "What I Like About You."
The Las Vegas-based band gave their latest single, "I Bet My Life," its network television debut, complete with lasers, smoke, fireworks and a choir.
Orange Is the New Black's Taylor Schilling and Uzo Aduba gave the award to Sam Smith. "I am awful at speaking in public, so I am gonna keep this really, really quick!" he said, thanking his fans. "Last year I wrote an album about being lonely, and tonight, I couldn’t feel further from lonely."
Glee's Dianna Agron and Castle's Nathan Fillion introduced Sam Smith's performance of "I'm Not the Only One" with a verse from A$AP Rocky.
Introduced by T.I. who declared, "Women can rap!," Iggy Azalea took the stage with Charli XCX for their hit, "Fancy" in a pair of power suits while at a press conference, complete with paparazzi-dressed dancers. She then swapped into a metallic jumpsuit for "Beg For It" among silver monkey bars.
Jhene Aiko and Meghan Trainor presented the award to Luke Bryan. "Thanks for making my dreams come true," he said after listing his thanks to everyone from God to his bus driver.
Introduced by The Hunger Games: Mockingjay, Part 1 actress Elizabeth Banks, Lorde performed the song she penned for the film, "Yellow Flicker Beat," initially from inside a small, red-lit room. She then emerged to front a stoic white-dressed group as she touted her now-signature dance moves.
Ariana Grande, in a black-lace gown, took the stage for piano-accompanied renditions of "Problem" and "Break Free," and was then joined by The Weeknd for "Love Me Harder."
Before introducing the pop/rock honor, Jenny McCarthy teased husband Donnie Wahlberg about winning the category's award 25 years ago, and even showed off a vintage photo and said, "That's right — I married that guy!" One Direction then claimed the award for Midnight Memories. "We had a lot of fun making the album, Midnight Memories, so thank you to anyone who bought it or even listened to it," said Harry Styles.
The host took a break to hit the stage for "Fireball" with a slew of female dancers and a portion of a silver globe behind him. Ne-Yo then joined him for "Time of Our Lives."
Khloe Kardashian Kendall Jenner and Kylie Jenner announced the category's winner to be Katy Perry, who accepted the award via video from Australia.
Imagine Dragons took home the honor for alternative rock. "To be a musician, there is no better career," said frontman Dan Reynolds.
Mary Lambert and Lucy Hale introduced the first live performance of "The Heart Wants What It Wants" by an emotional Selena Gomez, who sang in front of black and white graphics accented with prickly gold wire and red rose petals, among other visuals.
Julianne Hough presented the award to 5 Seconds of Summer.
Olivia Munn and Train's Pat Monahan gave the award to Azalea. "Musicians, we receive so much critique, some time you question what you're doing, and this validates that I'm on the right path."
Kate Beckinsale introduced a field-set performance of "Night Changes" by One Direction.
The couple hit the stage to perform "Start a Fire" together.
The two women in white gathered around a grand piano for "Bed Of Lies."
Before presenting the first-ever honor to Taylor Swift, Diana Ross first noted Dick Clark's pioneering ways for musicians: "He opened doors for us, he was a trailblazer, he was a legend."
Upon accepting the award, Swift applauded the legacies of Ross and Clark, and thanked her fans for their support during her anti-Spotify stance: "What you did by going out and investing in music and albums is you're saying that you believe in the same thing that I believe in, that music is valuable and should be consumed in albums, and albums should be consumed as art and appreciated."
Husband Josh Duhamel introduced Fergie's colorful performance of "L.A.LOVE (la la)" with YG and DJ Mustard.
After Garth Brooks shared a satellite performance from North Carolina's Greensboro Coliseum of "People Loving People," Ella Henderson and Aloe Blacc introduced Mary J. Blige's vintage-inspired performance of "Therapy," which she co-wrote withSam Smith.
The Shark Tank cast awarded the honor to Brantley Gilbert for Just as I Am.
Introduced by Pentatonix, Jessie J danced with Khloe Kardashian, Taylor Swift and Lorde before joining a gold-clad Ariana Grande and Nicki Minaj onstage during "Bang Bang."
Heidi Klum gave the award to One Direction, their third of the night.
The two singers, dressed in glittering jumpsuits, closed the show with their duet, "Booty," complete with Jennifer Lopez's disco ball dance break (and rejected booty call).
The 2014 American Music Awards are produced by Dick Clark Productions, a sister company of The Hollywood Reporter.