"Crazy in Love" is a song by American R&B singer–songwriter Beyoncé Knowles, featuring American rapper Jay-Z. Knowles, Jay-Z, and producer Rich Harrison wrote the song for Knowles' debut solo album, Dangerously in Love. The track features a sample from The Chi-Lites' 1970 song "Are You My Woman (Tell Me So)" that serves as the song's horn hook.

Released on July 8, 2003 as the album's lead single, "Crazy in Love" has reached number one on the charts of United States and the United Kingdom, and the top ten of many charts worldwide. "Crazy in Love" was critically acclaimed and has earned Knowles several awards. In 2009, British magazine NMEvoted the song as the best song of the decade. The song was also ranked at number three on Rolling Stone's 100 Best Songs of the Decade, number four on Pitchfork Media's list of The Top 500 Tracks of the 2000s, number seven on a list produced by The Daily Telegraphand number six on Slant Magazine's list of the 100 Best Singles of the Decade. The song won Best R&B Song and Best Rap/Sung Collaboration at the 46th Grammy Awards.

In 2002, Knowles had already recorded numerous songs for Dangerously in Love. Her management scheduled the album for an October 2002 release, however it was postponed several times to capitalize on the success of American rapper Nelly's single "Dilemma", which features Destiny's Child group mate Kelly Rowland. These delays allowed Knowles to go back to the studio and record more songs.

Rich Harrison had already prepared a demo of "Crazy in Love" (originally called 'Crazy Right Now') before he met Knowles. He recalled: "Yeah, I had it in the chamber, I hadn't really shopped it much, because sometimes you don't want to come out of the bag before it's right. People don't really get it and you'll leave them with a foul taste in their mouth. So it was just something that I held on to until I got the call from B."

Knowles was introduced to Harrison three months before the song was recorded. In the studio, Harrison played the demo for Knowles. After listening to the sample, Knowles asked Harrison to write the song, giving him two hours. The theme came from Knowles speaking of being conscious of her appearance. She kept saying "I'm looking crazy right now" and Harrison sang that back to her.

Knowles' boyfriend, American rapper Jay-Z became involved late into the song's production. Around three in the morning, he came to the studio and recorded a rap verse, which he thought up in about ten minutes but had not written down.

"Crazy in Love" is a love song composed in the key of D minor. The song's tempo is set at a moderate 100 beats per minute, in common time. Knowles' vocal range spans around one and a half octaves in the song, from A ₃to F ₅. "Crazy in Love" builds a song out of two major chords, B♭ and G, a third apart. One of the main vocal riffs uses the traditional cowbell rhythm that is often found in samba music and the like. Aside from its go-go vibe, "Crazy in Love" has also old soul influences that is derived from the horn hook. The hook is sampled by Harrison from the 1970 song "Are You My Woman? (Tell Me So)", originally recorded by the Chicago-based vocal group The Chi-Lites.

The lyrics of "Crazy in Love" is composed in the traditional verse-chorus form. Jay-Z opens the song with a brief spoken lyrics. After Knowles sings "uh-oh, uh-oh", he continues the monologue. Knowles begins the first verse, followed with the chorus. She repeats the "uh-oh, uh-oh" phrase, leading to the second verse. The chorus follows, giving way to the second rap. The song continues to the bridge, chorus, then fades out with the horns.

"Crazy in Love" was lauded by reviewers. Tim Sendra of Allmusic, an online music database, described the song as a "stunning pop masterpiece", while Stephen Thomas Erlewine of the same website called it "deliriously catchy". Darryl Sterdan, writing for the Canadian website Jam!, noted the song's "instantly addictive horn lines". Anthony DeCurtis for Rolling Stonemagazine also remarked to the horn sample, and noted the contribution of Jay-Z, writing: "'Crazy in Love' ... roars out of the speakers on the strength of a propulsive horn sample and the charged presence of her pal, Jay-Z." Marc Anthony Neal of the international webzine Popmatters complimented the "uh-oh, uh-oh" phrase as "catchy". MTV News considered the song the "proudest moment" of the album. "Crazy in Love" is ranked second in the list of biggest-selling singles since the year 2000 produced by Yahoo!.

In 2004, Knowles received three Grammy Awards nominations for "Crazy in Love", in the categories of Record of the Year, Best R&B Song, and Best Rap/Sung Collaboration, winning the last two. The award for Record of the Year was won by Coldplay's "Clocks". A remix of "Crazy in Love" known as "Krazy in Luv" (Maurice's Soul Nu Mix) won the award Best Remixed Recording, Non-Classical for its remixer, Maurice Joshua. It was also recognized at the 2004 ASCAP Awards as Most Performed Songs and its publisher, EMI, received the Publisher of the Year accolade. Vibemagazine's VIBE Awards also recognized the song for Coolest Collabo in 2003. In Europe, "Crazy in Love" won the award for Best Song at the 2003 MTV Europe Music Awards. The song has also been recognized by Knowles' peers in the urban markets, and won the award for Best Collaboration at the BET Awards in 2004. Entertainment Weeklymagazine ranked "Crazy in Love" 47 in the list of The 100 Greatest Summer Songs.

In 2002, Knowles signed with beverage company Pepsi. Subsequently, she appeared on various advertising campaigns of the company's product, and, in one of those promotional footages, the song "Crazy in Love" is being used as background music. "Crazy in Love" was included on the official soundtracks to the 2004 romantic comedy film Bridget Jones: The Edge of Reason. In 2004, it was also featured in the soundtracks of American comedy film White Chicksand Taxi, the Hollywood remake of the French film. The 2007 comedy film Good Luck Chuckused "Crazy in Love" in its soundtrack.

"Crazy in Love" was a commercial success in the United States. Although not yet served to retail stores, the single was already gaining massive attention. The single reached number one on the Hot 100, the official US singles chart, based on heavy rotation alone. The same week it reached number one, Dangerously in Lovedebuted on the 200 at number one as well. The substantial airplay, and later in retail, gains of "Crazy in Love" facilitated it to dominate the chart, subsequently spending eight straight weeks atop the Hot 100, making it Knowles' first #1 single in her solo career. Beyonce quickly outdid herself with the release of the album's second single, "Baby Boy", which topped the chart one week longer than "Crazy in Love." The single charted for twenty-seven weeks on the Hot 100, spending fifteen of those weeks in the top ten, and twenty-six of those weeks in the top fifty. The song was certified gold by the Recording Industry Association of America in 2004 for 500,000 digital downloads. In 2006 its Mobile Mastertone was also certified gold. "Crazy in Love" eventually became the fourth biggest hit of 2003 in the United States.

In international markets, "Crazy in Love" fared as well. Knowles made history being the second female artist to have a number-one single and a number-one album simultaneously in the UK. The first was Australian pop singer Kylie Minogue in 2001 with her album Feverand its single "Can't Get You out of My Head". Counting her career with former group Destiny's Child, this becomes her third number-one single in the UK and "Crazy in Love" was the only song to top the charts in both the UK and US in 2003. The single spent three weeks at number one in the UK,(370,000) and reached the top ten in many European countries. It reached number two in Australia; "Crazy in Love" was certified platinum by the Australian Recording Industry Association with sales in excess of 70,000 units, and emerged as the twenty-eighth best-selling single in Australia.

The music video of "Crazy in Love", released in May 2003, was filmed by English director Jake Nava. The video showcases Knowles in various dance sequences. The opening scene begins with Knowles wearing a tank top, short shorts, and red high-heels. She performs an elaborate solo dance on a riser. The scene shifts to a gold set detailing a mock photo shoot, before moving into a scene with dancers detailing Knowles and dancing against a wall while wearing caps and full length pants. Jay-Z then appears and ignites a line of petrol leading to a car which then explodes into flames. He proceeds to perform his rap in front of the burning car, and Beyonce dances and gyrates beside him, wearing an exotic silk print over a fur coat, before kicking the valve off a fire hydrant. She continues to dance while the water is flying all over the place. The video ends with Knowles and her dancers in front of a giant fan in vibrant dresses in contrast to the more neutral colors of the background, the video also had Carmit Bachar (one of the former Pussycat Dolls) as one of the dancers.

The music video received acclaim from critics, and won three awards at the 2003 MTV Video Music Awards in the categories of Best Female Video, Best R&B Video, and Best Choreography.

The song has various remixes, including the Rockwilder remix, Maurice's Nu Soul remix, and Juniors World remix. These versions appeared on the single releases of "Crazy in Love" under an altered spelling, "Krazy in Luv". British close harmony trio The Puppini Sisters have recorded a version of the song on their 'The Rise of Ruby Woo' album - a cover version further remixed by English electronica jazz outfit The Real Tuesday Weld. A version of the song included on Asian releases of Dangerously in Lovefeatures a rap in Mandarin Chinese performed by American-Taiwanese singer Vanness Wu, in lieu of Jay-Z's performance.

Since the song's release, many artists have recorded cover versions. In 2003, Irish singer-songwriter Mickey Joe Harte recorded an acoustic rendition of "Crazy In Love" for the charity album Even Better Than the Real Thing Vol. 1. Alternative rock band Snow Patrol covered the song on a BBC session with Zane Lowe. The cover was released as a b-side to the single "Spitting Games" and was later included on the compilation Cosmosonica - Tom Middleton Presents Crazy Covers Vol. 1. David Byrne performed "Crazy in Love" live, at the Hollywood Bowl in 2005. In 2007, American alternative rock band Switchfoot produced a rock version released in part of Yahoo!'s CoverArt series. While maintaining the fundamental elements of the track, Switchfoot added their "rock flavor" in it. The band shot a video for the cover version and is available on the Yahoo! Pepsi Smash website. After performing the song on air on the Australian radio station Triple J, The Magic Numbers recorded a cover for the 2007 Starbucks (Hear Music) compilation album, Sounds Eclectic: The Covers Project. British close harmony trio The Puppini Sisters covered the song for their 2007 album The Rise and Fall of Ruby Woo. Indie artist Dsico recorded an electronic music style cover of the song, which is available for download on the Internet. German group The Baseballs covered the song in rockabilly style for their debut album Strike!in 2009. Antony and the Johnsons released an orchestral take of the song as the b-side to their 2009 "Aeon" single.

This song was number three on Rolling Stone's 2009 list of the 50 Best Songs of the Decade. And number one on NME's " Tracks Of The Decade"