"Wake Me Up When September Ends" is a song by American rock band Green Day, released on June 13, 2005 as the fourth single from the group's seventh studio album, American Idiot (2004). The song was written by frontman Billie Joe Armstrong regarding the death of his father. The song's music video depicts a couple broken apart by the Iraq War, which was intended to convey the song's central theme of loss.
The song became a hit single, peaking at number six on the Billboard Hot 100. It was also a top ten single in the United Kingdom, Belgium, New Zealand, and was a number one single in Canada and the Czech Republic. In the United States, the song became symbolic after Hurricane Katrina, where it was dedicated to victims of the disaster. The song became the fourth single from American Idiot to be certified platinum by the Recording Industry Association of America.
"Wake Me Up When September Ends" was written by Green Day frontman Billie Joe Armstrong about his father, who died of cancer when he was ten. Armstrong at one point dubbed the song the most autobiographical he had written to that point, considering it "therapeutic" but also difficult to perform.
The song is largely unrelated to the storyline that is central to American Idiot.
The single peaked at number six in the United States, becoming Green Day's second Top 10 single. It also peaked at #8 in Canada and the UK, while making #13 in Australia. "Wake Me Up When September Ends" had sold 1,652,000 copies as of May 2010, and was the second highest selling single in the U.S. from American Idiot, behind only the multi-platinum "Boulevard of Broken Dreams". The song ended the streak of Green Day's three consecutive #1 hits on the Modern Rock Tracks chart ("American Idiot", "Boulevard of Broken Dreams" and "Holiday"), but it hit #2 on the chart, kept from #1 by Gorillaz "Feel Good Inc.". The song also hit #2 on the Adult Top 40 and #4 on the Mainstream Top 40. This was the band's most successful song to the adult contemporary market, hitting #13 on its own chart and their only song to chart other than "Boulevard of Broken Dreams". The song is certified Silver in the United Kingdom for sales of 200,000 
The song's music video was directed by Samuel Bayer, best known for his work with Nirvana and Metallica. Bayer wrote the treatment for the video, which he envisioned as a mini-movie. Bayer brought the idea of an Iraq War-themed video to the trio after interviewing soldiers who had signed up to fight after being persuaded by a television advertisement. The song's music video thusly attempts to "turn the machine on itself" by acting as a commercial for "free thought or peace." Although it was far from the song's literal meaning, Armstrong felt it appropriate considering the song's theme of loss. Bayer noted that he felt bored with predictable music videos, and wanted to produce a video that felt like a film. Consequently, he and a crew spent a month casting actors for the roles and conducted rehearsals, uncommon for music videos. The clip was filmed in Los Angeles in late March 2004.
The video focuses on a couple in love (played by Jamie Bell and Evan Rachel Wood). The boyfriend promises never to leave his girlfriend but they later argue when the boyfriend enlists in the United States Marine Corps. The boyfriend interprets his actions as a way to show her that he loves her so much that he would put his life on the line to keep her safe; the girlfriend, however, is heartbroken, as he broke his vow to never leave her, and terrified at the thought that he might die in battle. The video then shows the boyfriend in battle in Iraq being ambushed by insurgents. This scene is intercut with scenes of the girlfriend tearfully mourning in a quiet field. The video ends on this juxtaposition, emphasizing the pain and heartache of losing loved ones due to the war.
The clip prompted criticism from conservative media pundits. On the subject of the clip being seen as exploitive of the war for entertainment purposes, Dirnt rejected this notion: "Rock & roll should be dangerous. […] It should be striking and stir questions, and I think that that video, at the end of the day, comes down to that core emotion of loss." Bayer considered it his best production to that point, remarking, "’September’ is hands down the greatest thing I’ve ever done."
"Wake Me Up When September Ends" became closely associated with Hurricane Katrina, which struck the Gulf Coast of the United States on August 31, 2005. "Wake Me Up When September Ends" became symbolic in the aftermath; one online blogger paired the song with television coverage of the disaster, creating a viral video. Green Day performed the song days after the disaster on ReAct Now: Music & Relief, a benefit concert broadcast on MTV and its associated properties.