The Guess Who was a Canadian rock band, originating as The Guess Who? in 1966, and adopting the name The Guess Who in 1968. Formed as a garage rock band,^[1] their best-known works are in the pop rock^[2] and psychedelic rock^[3] genres.

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They were most successful from 1969 to 1975, under the leadership of singer/keyboardist Burton Cummings. During that period they released eleven studio albums, all of which reached the charts in Canada and the United States; their 1970 album American Woman reached no. 1 in Canada and no. 9 in the United States, and five other albums reached the top ten in Canada. They also achieved five number one singles in Canada and two in the United States.

Note that almost all of the band's early tracks, originally issued by "Chad Allan and the Reflections", "Bob Ashley and the Reflections" or "Chad Allan and the Original Reflections", were later re-issued on albums that were jointly credited to "Chad Allan & the Expressions"/"Guess Who?" (i.e. both group names appeared on the album cover).