"It Girl" is a song by American recording artist Jason Derulo, released as the second single from his second studio album, Future History on August 9, 2011. The song was written by Derulo, E. Kidd Bogart, Lindy Robbins and Emanuel "Eman" Kiriakou, who also handled the song's production. Musically, "It Girl" is a mid-tempo pop and R&B love song, that features a whistling intro and an acoustic guitar melody. Lyrically, it revolves around Derulo singing the praises of the perfect girl he found after searching all over.

The song received positive reviews from music critics, who praised its catchy production and radio-friendly lyrics. They also added that it has the potential to overshadow the commercial success of Derulo's debut single, "Whatcha Say" (2009). "It Girl" peaked at number 17 on the US Billboard Hot 100, number six on the US Hot Dance Club Songs chart, and at number 10 on the US Pop Songs chart. Outside of the United States, "It Girl" peaked within the top ten of the charts in Australia, Denmark, New Zealand, the Republic of Ireland, and the United Kingdom, and peaked within the top 20 of the charts in Hungary, Japan, the Netherlands, and Norway.

The accompanying music video of "It Girl" was directed by Colin Tilley and filmed at a mansion in Malibu, California. It portrays a fictional relationship between Derulo and his love interest played by actress Tika Sumpter. To promote the song, Derulo performed the song live on televised shows, including America's Got Talent, The Wendy Williams Show, The Ellen DeGeneres Show and The X Factor Australia. The official remix of the song premiered online in February 2012, and features Derulo's former girlfriend Jordin Sparks.

"It Girl" was written by Jason Derulo, E. Kidd Bogart, Lindy Robbins and Emanuel "Eman" Kiriakou, who also produced the track. The engineering process was handled by Jens Koerkmeier. It was mixed by Serban Ghenea at Mixstar Studios in Virginia Beach, Virginia. The song's keyboards, whistle, guitars, bass, percussion and drum programming were provided by Eman, with additional keyboards and drum programming by Koerkmeier and Andrew Goldstein. On July 29, 2011, the audio of "It Girl" was uploaded to Derulo's official YouTube account. When speaking of the song, Derulo told The Daily Telegraph, "I wanted to put myself in a position as if I'd found my It Girl, to make myself feel like if I found that one true love. I've basically described what it would be like if I found her." Derulo further elaborated about the concept of the song in another interview with Matt Elias of MTV News:

An 'It Girl' to me is someone who is selfless, someone who's always thinking about others before she thinks about herself. You know, my mom is a very charitable woman, so I'd want someone who is in line with that kind of thought process. I also like a girl who's polite. I feel like that's a lost art, and just saying 'please' and 'thank you' goes a very long way with me. That's just so lost these days. So, ladies, it's OK to say 'thank you.'

Derulo explained that he did not believe in the possibility of "It Girl" to be the next single from Future History. However, his peers believed that it was very distinct from the lead single, "Don't Wanna Go Home" and that response motivated him to pick it as the second single. He believed that showing the difference in the new album was important in picking the single. He did not want to put another dance song so that his fans do not assume that the entire album consisted of uptempo songs. He concluded that "growing up has definitely taken place. My music has always been a representation of who I am and I guess I speak differently, my demeanour is different."

"It Girl" is a mid-tempo pop and R&B love song, built on a finger-clicking beat. The song is set in common time with a moderate tempo of 95 beats per minute. It is composed in the key of E major with Derulo's vocal range spanning from the note of E₃ to the note of B₄. According to Rap-Up, the song's lyrics find Derulo as the male protagonist singing praises of "a lovely lady", comparing her to his "greatest hit". "It Girl" opens with a whistling intro and an acoustic guitar melody. In the first verse, he chants about how he searched all over and finally found the girl of his dreams. He also affirms that the girl means much more than a Grammy Award to him. Its hook, which forms part of the chorus, contains the lyrics: "You could be my it girl / Baby, you're the shit girl / Lovin; you could be a crime / Crazy how we fit, girl / This is it, girl / Gimme 25 to life / I just wanna rock all night long and put you in the middle of my spotlight / You could be my it girl / You're my biggest hit, girl / Let me play it loud." Scott Shelter from Pop Crush noted that the song uses the "oh-oh-oh-oh" vocal chants after the chorus.

"It Girl" was added to the B-playlist of urban radio station BBC Radio 1Xtra in the United Kingdom on August 5, 2011. The song was released as a digital download on iTunes Stores worldwide from May 6, 2011. "It Girl" impacted contemporary hit radio in the United States on August 16, 2011, and mainstream radio in the UK on August 24, 2011. A digital extended play with four remixes of the song, was released in Denmark, Ireland, Switzerland and the United Kingdom on September 16, 2011. "It Girl" was made available as a CD single in Germany on November 25, 2011. On February 29, 2012, the official remix of "It Girl" premiered online, which features Derulo's former girlfriend Jordin Sparks. The remix has a slower tempo than the original and features a new verse by Sparks. Cristin Maher of PopCrush noted that both singers "harmonize together on the chorus, with their voices matching up beautifully". The remix was accompanied by a video that displays behind-the-scenes footage of Derulo and Sparks spending time together.