The group's fifth studio album, The E.N.D, title that stands for "The Energy Never Dies", was released on June 9, 2009. The overall sound of the album has a more electro hop beat rather than the usual hip pop/R&B feeling of their previous albums. Following its release, will.i.am remarked that the album had been inspired by a trip to Australia, specifically the sound of The Presets' "My People". "The energy on the Presets' small little stage was crazy energy. That song My People – that shit is wild," will.i.am said, "That's the reason why this record sounds the way it does – my three months in Australia." In its first week, the album sold 304,000 copies and debuted at number 1 on the Billboard 200. In the United States, the album became the ninth album to top the one million mark in sales in 2009. The album spent 38 weeks within the top 10 of the Billboard 200. The E.N.D was the 7th best-selling album of 2009 in the U.S. It also debuted at number one in Australia, number two in New Zealand and three in the United Kingdom. Three additional singles, "Imma Be", "Alive", and "Meet Me Halfway", were released through the iTunes Store in the three weeks running up to the album's release.
The first single "Boom Boom Pow" was released on March 30, 2009 in the U.S. on iTunes. The single sold 465,000 downloads in its first week of digital release, the third-largest number of download sales in a single week overall, and the largest single-week and debut-download totals by a group in the history of digital-download sales, reaching No. 1 on the U.S. The single also reached the top spot in Billboard Hot 100 and Pop 100. being the group's first U.S. No. 1, holding the spot for twelve consecutive weeks. It also reached number 1 in Australia, Canada, and the UK. On May 21, the Black Eyed Peas released "I Gotta Feeling" (produced by David Guetta) as the official second single from the album. The single charted at number three and then went to number one on the UK Singles Chart. It debuted at number 2 on the Billboard Hot 100 behind "Boom Boom Pow" and later surpassed it, taking the number 1 spot. The Black Eyed Peas joined a group of artists who have held the No.1 and 2 Spot on the Billboard Hot 100 simultaneously. From April 18, 2009, when "Boom Boom Pow" reached No. 1, through October 10, 2009, the last week "I Gotta Feeling" was at No. 1, the group was on top of the chart for 26 weeks, more consecutive weeks than any other artist.
On July 30, 2009, Billboard announced that the Black Eyed Peas set a record for the longest successive No. 1 chart run by a duo or group in the Billboard Hot 100's history. "I Gotta Feeling" hit its fifth consecutive week at No. 1, following 12 weeks at the top by the Peas' "Boom Boom Pow"; Boyz II Men reigned on the chart for two 16-week runs in the mid-'90s. "Meet Me Halfway" was released as the third single from the album in September 2009. The single reached number one in the UK and Australia, making it their third chart topper from The E.N.D in both countries. It also peaked at seven on the U.S. Billboard Hot 100, making it the group's third top-10 single from The E.N.D "Imma Be" was released as the fourth single in the U.S. on December 15, 2009, reaching number one on the Billboard Hot 100 for two weeks, becoming the group's third number one single on that chart. Heavy airplay in Canada caused "Imma Be" to reach number 5 on the Canadian Hot 100, their fourth consecutive top-five hit from the album. "Rock That Body" was then released as the fifth single, and has so far reached number nine on the Billboard Hot 100.
In September 2009, the group embarked on The E.N.D World Tour, visiting Japan, Thailand, Malaysia, Australia, and New Zealand. In October 2009, they also were the opening acts for 5 concerts of the U2 360° Tour North America leg. The group performed at the Grammys on January 31, 2010. They performed a mash-up of "Imma Be"/"I Gotta Feeling". They won three awards out of the six nominations, including Best Pop Vocal Album for The E.N.D., Best Pop Vocal Performance by a Group for "I Gotta Feeling", and Best Short Form Video for "Boom Boom Pow".
On September 8, 2009, the group performed live for Oprah Winfrey's 24th Season Kickoff Party, on Michigan Avenue in Chicago. An estimated 21,000 dancers in the streets performed a flash mob to the live performance of "I Gotta Feeling". The group performed at the American Music Awards of 2009 with the songs "Meet Me Halfway" and "Boom Boom Pow". They also won 2 out of 3 categories in which they were nominated; Favorite Rock/Pop Group & Favorite R&B/Soul Group.