Songfacts®:

• This upbeat dance anthem is the second single from Britney Spears' seventh album Femme Fatale. The song was written by Kesha and produced by Dr. Luke and Max Martin. It was released on March 14, 2011.
• Speaking about the song, Kesha told Spin magazine: "That song is me imagining her and any female musician touring the world. You know, when you go out, and you're having an amazing, magical night and you don't want to go to sleep and you want it to last until the world ends."
• A pre-famous Kesha previously worked with Spears on her Circus song, "Lace and Leather." "I just did backgrounds for her 'cause I was so broke. I needed to pay my rent," the TiK ToK singer told MTV News in 2009. "I got a few bucks. No, [I didn't meet her]. I just did backups for her."
• Most of the tracks on Femme Fatale are dance numbers. Spears admitted in an interview with V magazine that she prefers to make tunes that will get fans out on the floor. "I like music that makes you move and connects with your soul. I like to feel inspired right away when I listen to new music," she said. "I always have songs being sent to me from new artists and producers from all over the world, which is really cool. From there I just follow my heart."
• Spears admitted in an interview on Ryan Seacrest's radio show that the song just felt right for her as soon as she heard it. " 'Till the World Ends' is fun! It's fun. I like it. It's good energy," she said. "I'm a vibe person, and I think I love good-mood songs, and if it puts me in a good mood, it clicks for me."
• When asked by Rolling Stone how she sees the studio relationship between Max Martin and Dr. Luke, Britney replied: "They are two peas in a pod. It's a total bromance."
• The post-apocalyptic music video was directed by Ray Kay and filmed in a clammy Los Angeles basement. The clip sees Spears dancing with her entourage on December 12, 2012, the date on which, according to the Mayan calendar, the world will end. It was the first time Spears had worked with the Norwegian director, who has also helmed visuals for the likes of Justin Bieber, Lady Gaga and Beyonce. Filming the clip was less than pleasant. "The set was a little much. It was grimy and gross and it felt like there was poop everywhere when there wasn't," Spears recalled to MTV News. "It was sweat and it was disgusting sometimes."
• A remixed version featuring Kesha and rapper Nicki Minaj was released on April 25, 2011. The remix starts with Minaj rapping with intensity about a female hater before Spears and Kesha take over. The remix also features a dubstep breakdown, that has been compared to the one in "Hold It Against Me." "I'm a massive fan of both the ladies I share the track with," Said Kesha to MTV News. "I wrote 'TTWE' for Britney with [producers] Dr. Luke and Max [Martin] and she killed it and I loved it, but I just thought a supergroup of three hot, strong women could just take over the airwaves."