"I Kissed a Girl" is a song by pop singer Katy Perry, written by Perry, Dr Luke, Max Martin and Cathy Dennis (not to be confused with the earlier song with the same title by Jill Sobule). It was produced by Dr. Luke for Perry's 2008 album One of the Boys. Perry says the song is "about the magical beauty of a woman".

Released as the album's lead single, "I Kissed a Girl" was a commercial success. It topped the Hot 100 chart, becoming the 1000th chart-topper of the Rock Era. The song has since become a major worldwide hit, and along with the United States, it has topped the charts in more than 30 countries, including Australia, Canada, Ireland and the United Kingdom.

"I Kissed a Girl" was performed and a nominee at the 51st Grammy Awards (Grammy Award for Best Female Pop Vocal Performance). It was also nominated for Favorite Song at the 2009 Kids' Choice Awards.

Perry has stated that "I Kissed A Girl is just a way for me to seem edgy and cool, I think it's worked." She says:

"Everyone takes the song and relates it to their situation, they can see it however they want to see it. Love it, hate it, for me it was about us girls. When we're young, we're very touchy-feeley. We have slumber party sing-a-longs, we make up dance routines in our pajamas. We’re a lot more intimate in a friendship than guys can be. It’s not perverse but just sweet, that's what the song is about..."

The song was partially inspired by Scarlett Johansson.

Perry has also stated that the song was inspired by a particular person,

"The song was inspired by a friendship I had with a girl when I was 15, but I didn't kiss her. I was totally obsessed with her. She was beautiful – porcelain skin, perfect lips – and I still talk to her, but I've never told her the song is about her."

A music video for the song was released on May 16, 2008 on Perry's personal website and on MySpace. The video was directed by Kinga Burza and features a Moulin Rouge and burlesque-type setting with scenes of Perry, along with many other flamboyantly-dressed women dancing to the song. Towards the end of the video, she wakes up next to a male companion called Derek (DJ Skeet Skeet). Despite the song's title, there is no depiction of same-sex kissing. Katy features her real life friend and DJ, Mia Moretti and her main guy, Markus Molinari's cat Bella and the singer Ke$ha in the music video.

The video made its television debut on June 12 on TRL with the visit and interview by Perry in set show. On June 24, 2008 it became #1 on TRL. The video obtained high airplay on this music video channel, as well as on VH1. It debuted at #20 on VH1's VH1 Top 20 Video Countdown on June 28, 2008. On June 30, 2008 the video was premiered on MTV Latin America. On July 6, 2008, it rose to #4 on VH1's VH1 Top 20 Video Countdown. The video received five nominations for the 2008 MTV Video Music Awards, including Best Female Video and Best New Artist. The video has had over 24 million views on YouTube. Due to the video and the song's popularity around the world, there are videos on YouTube which imitate and parody the song.

"I Kissed a Girl" has drawn mixed reviews from critics. Blogcritics Magazine called it "an instantly catchy number", and About.com said, "fueled by an instrumental wallop provided courtesy of producer Dr. Luke, 'I Kissed a Girl' is the perfect breakthrough". However, Rolling Stonemagazine, while giving her album 2/5 stars, described the song as a "New Wave-y club single", saying the supposedly rebellious "attention-grabbing" lyrics are "a vanilla recounting of her chick-on-chick exploits" and that this "acting out" is "just to get a dude's attention". This song was number 20 on Rolling Stone's list of the 100 Best Songs of 2008. Allmusic praises "the stomping Gary Glitter beat" before criticizing the producers for turning it "into a leaden stumble and burying Perry's voice underneath Pro Tools overdubs so it all winds up as a faceless wash of sound designed to be placed in TV shows, movie trailers, and malls".

Sal Cinquemani of Slantmagazine wrote, Perry's "lead single "I Kissed a Girl" features a throbbing beat and an infectious, bi-curious hook, but its self-satisfied, in-your-face posturing rings phony in comparison to the expertly constructed ambiguities of "Justify My Love" or practically anything in the first decade of Ani DiFranco's catalog; it's like a tween version of DiFranco's tortured bisexual confession "Light of Some Kind"". Hiponline.comwrote that the song is "not nearly as interesting or exciting as you’d expect. It’s not even half as good as Jill Sobule’s song 'I Kissed a Girl'". Glitterati Gossipagrees Sobule's song "was ten times better, because there was actual emotional content to her lyrics".

Sobule shared her feelings about Perry's song and use of the title in a July 2009 interview with The Rumpus:

As a musician I have always refrained from criticizing another artist. I was, 'Well, good for her.' It did bug me a little bit, however, when she said she came up with the idea for the title in a dream. In truth, she wrote it with a team of professional writers and was signed by the very same guy that signed me in 1995. I have not mentioned that in interviews as I don't want to sound bitter or petty...

Okay, maybe, if I really think about it, there were a few jealous and pissed-off moments. So here goes, for the first time in an interview: Fuck you, Katy Perry, you fucking stupid, maybe 'not good for the gays,' title-thieving, haven't heard much else, so not quite sure if you're talented, fucking little slut.

AllMusicconcluded "the problem is not with Katy's gender-bending, it's that her heart isn't in it; she's just using it to get her places, so she sinks to crass, craven depths". Slant Magazineagrees, saying the song "isn't problematic because it promotes homosexuality, but because its appropriation of the gay lifestyle exists for the sole purpose of garnering attention — both from Perry's boyfriend and her audience".

Adam Holz of PluggedinOnline, a division of Focus on the Family, wrote an article entitled "A Tale of Two Katys" about the singer's image transformation from a Contemporary Christian Music artist to one of the "girls gone wild". He criticizes the song for being the latest, "high-profile message to young women and men that our sexuality is a malleable commodity that can be reshaped at will". Holz also argues that Perry's message carries with it "no need to worry about who might get used or objectified in the process", causing Perry to live "down to a damaging, demeaning stereotype".

In some areas of the world the song's lyrics have kept it from reaching the Top 40 or to even be released at all. Though the Toronto Stardescribes it as "a lesbian-friendly tune", whether homophobia fuels negative reactions to the song or the song itself appears to divide critics. Slantand other critics suggest that Perry may be homophobic, especially given her single "Ur So Gay", which makes "I Kissed a Girl" seem like "a classic example of the 'Guys kissing is gross, girls kissing is hot' line of thought". The Star Ledgerquotes a listener who proposes that negative reactions to the song are due to homophobia, saying that it would not draw disapproval if sung by a male artist, and who compares the level of explicitness in the lyrics with other songs on the radio such as rap lyrics. MomLogic.comwriter Vuv-A-Licious agrees, asking "What's the big deal? ...When this tune is playing and my son and daughter are dancing, I will be trying to dance along, or trying to acknowledge that they may one day dance to the beat of a different drummer than me".

In an August 2008, interview with the Daily Mail, Perry's mother, Mary Hudson, an evangelical Christian preacher, was reported as saying that she disliked the song, stating "It clearly promotes homosexuality and its message is shameful and disgusting...". However, Perry took to her official blog stating that her mother's supposed comments were completely fabricated, while also saying her parents love and support her and attend many of her shows.

Regarding the question of her own sexuality that the song has raised, Perry told Santa Barbara magazine "I like to kiss boys, but there is no doubt in my mind if Angelina Jolie or Gisele Bündchen came a callin', who wouldn't pucker up?". In an interview on the blog The New Gay, Perry admitted she has never actually kissed a girl and is heterosexual. She is quoted as saying "Yeah, it’s fantasy, it’s a song about curiosity." However, in a separate interview, Perry stated that she has kissed a girl.

In February 2009, Márcio Barros, a substitute English language teacher in a Distrito Federal, Brazil public school was fired after he used the song in a class activity among students ages 12 to 14. He was accused of promoting "homosexualism" and alcoholic beverages usage through the lyrics of the song. The Secretary of Education supported the decision of the head of the school.

"I Kissed a Girl" debuted at number 76 at Billboard Hot 100. After a couple of weeks, the single hit the top 5, due to the rising digital downloads and increasing radio airplay. It continued to rise the next week, reaching #2 just behind her labelmate, Coldplay. The following week, the song reached the summit of the US chart, becoming the 1000th #1 song of the rock era (the 961st #1 on the Billboard Hot 100). In addition the song also gave the Capitol label two consecutive Hot 100 #1's, as the week's prior #1 was fellow Capitol artist Coldplay's "Viva La Vida", making it the first time since 1976 Capitol has had two back to back chart toppers on the Hot 100. The single also crossed over to Billboard's sister publication R&R's Rhythmic chart in its July 5 issue, where not only did she have the highest debut ever for a non-rhythmic track, entering at number 26 with 1,065 spins, she also had the highest debut from a new artist in over five years. The bow is the best for a debut track at Rhythmic since Beyoncé entered at No. 21 with "Crazy In Love" in 2003. It also became the first song since Gnarls Barkley's "Crazy" to simultaneously appear on the Mainstream Top 40, Rhythmic, Adult Top 40 and Alternative charts. On July 26, 2008, the track also made history by reaching the number one spot on Billboard's Hot Dance Airplay chart by three weeks, a first for a solo act with a debut single. The song topped the Hot 100 for seven weeks in a row before finally being dethroned by Rihanna's "Disturbia". It is the second longest running number one on the Hot 100 of 2008 (tied with "Whatever You Like"), with only Flo Rida's "Low" topping the chart for longer. According to Official UK Singles Chart, the single has sold over 535,000 copies in the United Kingdom as of January 25, 2009, is the first Virgin label single to sell more than half a million copies since the Spice Girls’ "Goodbye" in 1998.

In Canada, the single debuted at #55 at Canadian Hot 100, reaching #1 on June 12 in a 26-position jump.

In New Zealand, the song debuted at number 38, the single's first appearance in other countries chart outside North America, moving to number three the following week. The song was certified Gold after seven weeks with sales of over 7,500. On August 11, 2008, eight weeks after debuting on the chart, "I Kissed A Girl" finally made it to number one. "I Kissed A Girl" was certified Platinum in New Zealand after 20 weeks selling 15,000+ copies.

In Australia, the song debuted at #13 on the 30th of June on downloads alone, then the next week jumped to second position behind Jordin Sparks, still on downloads alone. The next week it jumped to number one still solely off downloads, becoming only the second single to do so. Ironically, by the time the song went number 1, this was the time when World Youth Day 2008 had started and the event held anti-gay views. On July 21, 2008, after the singles physical release, the track retained its number one position and was certified Gold. The single has held the number one position for several weeks and was certified 2× Platinum.

In the United Kingdom, a cover version released by the artist Nicki Bliss was climbing up the UK iTunes Chart. It debuted on the UK Singles Chart (published August 3, 2008) at position number 50.

A second cover version, by Barnicle, entered the UK Singles Chart (published August 3, 2008) at position #116.

Because of the success of the cover versions, the official release of Katy Perry's version was brought forward from September 1 to July 30, 2008. On August 3, 2008, the song, which had entered the UK Singles Chart at number 139 the week before, climbed 135 places to reach position number 4. The song has become one of the most requested on Radio 1's request hour. The following week it climbed 3 places to reach number 1. The following week it stayed at the top spot for a second consecutive week and then went on to spend 5 consecutive weeks at #1.

Even parodies of "I Kissed a Girl" are seeing chart success. Dr. Demento ranked Robert Lund's spoof "I Peed in the Pool" his #1 song of August, 2008, and one of his Funny 25 for the year. The song climbed back into the top 20 (reaching #19) in the UK on January 4, 2009, five months after it was first released.