Stadium Arcadium (2005-2006)

Again working with producer Rick Rubin, they completed their ninth studio album, Stadium Arcadium, in 2005. Although 38 songs were created, it was released as a 28-track double album, originally intended to be released as 3 mini-albums spaced six months apart. The first disc in the set is titled "Jupiter", while the second is called "Mars", which both contain 14 songs. The record contains some of the heaviest material the band has ever made as well as having the harmonious and textured sounds similar to the ones featured on their previous two albums.

The band performed some of their new material live in concerts in Atlantic City, Las Vegas, New York, and in Los Angeles. The album was released on May 9, 2006 in North America (May 8 in Europe) with a world tour being launched in New York to support it. The first single is called "Dani California", according to Kiedis the same girl from songs "By The Way" ("Dani the girl") and "Californication" ("Teenage bride with a baby inside") are representative of every girl he has ever known.

In February 2006, the band announced the first dates of the Stadium Arcadium world tour, with the first dates being announced in Europe. The band announced dates in Spain, Germany, France, the Czech Republic and most notably 13 dates altogether in the UK (Four nights in London). The band also scheduled to play festivals such as T in the Park in Scotland, Rock In Rio in Portugal and Oxegen in Ireland, as well as Lollapalooza in Chicago, IL, USA. The band has announced that they are beginning a US tour in August 2006.

On April 4, 2006, the band's first single "Dani California" from Stadium Arcadium was released as a download, the single released followed 4 weeks later on May 1, 2006, and a week later the 7" Picture disc was released, on the day of Stadium Arcadium's official release. On April 29, the full album was leaked onto the internet.

On April 15, the band performed a free open air gig at BBC Television Centre in White City, London. The gig was free to people who entered a competition by the rock magazine Kerrang! and the Red Hot Chili Peppers' website. They performed Dani California and a host of new tracks off their new album and a couple of old songs for a special recording of popular chart show Top of the Pops shown on Sunday, April 16 at 1900 on BBC2, this caused problems because the BBC didn't have a license for the concert.

On May 6, 2006, they performed "Dani California" and "Give It Away" on the television program Saturday Night Live to help promote their new CD. For the same purpose, the band will also perform at the 14th annual KROQ Weenie Roast.

On June 17, 2006, in Japan, the movie Death Note will come out in Japan with "Dani California" as its theme song.

Runner's World Magazine announced that Stadium Arcadium was the top workout album for 2006