Chicago (retroactively known as Chicago II) is the second studio album by Chicago-based American rock band Chicago. Like their debut album, Chicago Transit Authority, this was a double album. It was their first album under the name Chicago (the band's prior name, Chicago Transit Authority, was changed due to a threatened lawsuit from the actual mass-transit operator bearing the same name) and the first to use the now ubiquitous cursive Chicago logo on the cover.

Released in January 1970 on Columbia Records, Chicago was commercially successful. It was certified gold by the Recording Industry Association of America (RIAA) in April of the same year of its release, and certified platinum in 1991. It reached No. 4 on the album charts in the United States and No. 6 on the album charts in the UK, and produced three top ten singles on the Billboard Hot 100. The album received three Grammy Award nominations - for Album of the Year, Contemporary Vocal Group, and Best Album Cover. It was voted best album of 1970 by readers of Cash Box magazine, and the 1971 best small-combo LP by readers of Playboy magazine.