"You Ain't Seen Nothing Yet" is a rock song written by Randy Bachman and first performed by Bachman–Turner Overdrive (BTO) for the album Not Fragile (1974). It was released as a single in 1974 with an instrumental track "Free Wheelin'" as the B-side. It reached the number 1 position on the Billboard Hot 100 singles chart and the Canadian RPM chart the week of November 9, 1974 as well as reaching number 2 on the UK Singles Chart.

The lyrics for the song tell of the singer meeting a "devil woman" and she giving him love. The chorus of the song includes the song's famous stutter and speaks of her looking at him with big brown eyes and [saying] 'You ain't seen nothin' yet. B-, b-, b-, baby, you just ain't seen na, na, nothin yet. Here's somethin' that you're never gonna forget. B-, b-, b-, baby, you just ain't seen na, na, nothin yet.'

"You Ain't Seen Nothing Yet" was written by Randy Bachman. In The Rolling Stone Record Guide, writer Dave Marsh called the song "a direct steal from The Who", but "an imaginative one." The chords of the chorus riff are very similar to the ones used by The Who in their song "Baba O'Riley", and also, the stuttering vocal is reminiscent of "My Generation". Randy insists that the song was performed as a joke for his brother, Gary, who had a stutter, with no intention of sounding like "My Generation". They only intended to record it once with the stutter and send the only recording to Gary.

Randy developed the song while recording BTO's third album, Not Fragile (1974). It began as an instrumental piece inspired by the rhythm guitar of Dave Mason. Randy says "it was basically just an instrumental and I was fooling around... I wrote the lyrics, out of the blue, and stuttered them through." The band typically used the song as a "work track" in the studio to get the amplifiers and microphones set properly.

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