Think Tank is the seventh studio album by the English rock band Blur, released on 5 May 2003. Continuing the jam-based studio constructions of the group's previous album, 13 (1999), the album expanded on the use of sampled rhythm loops and brooding, heavy electronic sounds. There are also heavy influences from dance music, hip hop, dub, jazz, and African music, an indication of songwriter Damon Albarn's expanding musical interests.

Recording sessions started in November 2001, taking place in London, Morocco and Devon, and finished a year later. The album's primary producer was Ben Hillier with additional production by Norman Cook (Fatboy Slim), and William Orbit. At the start of the sessions, guitarist Graham Coxon had been in rehab for alcoholism, so was not present. Initially unaware of how long Coxon would be in rehab for, Albarn, James and Rowntree decided to start work in the studio without Coxon.

After he re-joined, relationships between him and the other members became strained. After initial recording sessions, Coxon left, leaving little of his presence on the finished album. This is the only Blur album to not feature Coxon as a full-time member; he reunited with Damon Albarn in 2008, resulting in Blur starting to play live again in 2009, and returned to the band for their next album The Magic Whip (2015).

Think Tank is a loose concept album, which Albarn has stated is about "love and politics". Albarn, a pacifist, had spoken out against the invasion of Afghanistan and, after Western nations threatened to invade Iraq, took part in the widespread protests against the war. Anti-war themes are recurrent in the album as well as in associated artwork and promotional videos.

After leaking onto the internet in March, Think Tank was released on 5 May 2003 and entered the UK Albums Chart at number one, making it Blur's fifth consecutive studio album to reach the top spot. The album was later certified Gold. Think Tank also reached the top 20 in many other countries, including Austria, Switzerland, Germany, Norway and Japan. It was their highest charting album in the United States at the time, reaching number 56 on the Billboard 200. The album produced three singles, which charted at number 5, number 18 and number 22 respectively on the UK singles chart. After the album was released, Blur announced a world tour with Simon Tong filling in for Coxon.

Although Blur had been associated with the Britpop movement, they had experimented with different musical styles more recently, beginning with Blur (1997) which had been influenced by indie rock bands under the suggestion of guitarist Graham Coxon. Since the mid to late 1990s, Blur's members had been working on other projects as well as Blur: Albarn had co-created Gorillaz, a virtual band, in 1998 with comic artist Jamie Hewlett whom Albarn had met through Coxon. Gorillaz' 2001 debut was financially successful and received critical acclaim. Since composing the Blur song, "You're So Great", Coxon had started a solo career and as of 2001 had released three solo albums. The members' differing musical interests had alienated some of the band members, with Coxon explaining, "we're all very concerned for each other and we do genuinely like each other an awful lot. Because we're into so much different stuff, it becomes daunting." Nevertheless, Coxon, along with Alex James and Dave Rowntree were keen for a new album, whilst Albarn was more reluctant.

Blur's prior album, 13, had made heavy use of experimental and electronic music with the guidance of producer William Orbit. Despite the success of the album and its associated singles, the overall sound of the album had been deemed as "deliberately uncommercial" compared to their previous efforts. Despite the broader musical landscaping which Blur were engaging in, Albarn said in a January 2001 interview that he wanted to make a more accessible album again, stating "I'm trying to go back to the kind of songwriting aesthetic I had on (hit album) Parklife. They won't be arranged in the same way at all – they'll just be songs that are accessible to the public." He also explained his reasoning for this approach, stating that "it's too complicated being anything other than mainstream with Blur. That's where it belongs. We still feel that the mainstream in Britain is not represented well enough by intelligent musicians."

After the September 11 attacks, a series of controversial military campaigns were launched, known as the war on terror. In November 2001, shortly after the Invasion of Afghanistan, the MTV Europe Music Awards were held in Frankfurt, where Gorillaz won an award for Best Dance Act. As Albarn and Hewlett walked onto stage to make a speech, Albarn sported a T-shirt with the Campaign for Nuclear Disarmament logo on it. In Albarn's speech, he said "So, fuck the music. Listen. See this symbol here, [pointing to the t-shirt] this the symbol for the Campaign for Nuclear Disarmament. Bombing one of the poorest countries in the world is wrong. You've got a voice and you have got to do what you can about it, alright?"