"You Ain't Seen Nothing Yet" is a rock song written by Randy Bachman and performed by Bachman–Turner Overdrive (BTO) on the album Not Fragile. It was released as a single in 1974 with an instrumental track "Free Wheelin'" as the B-side. It reached the #1 position on the Billboard Hot 100 singles chart the week of November 9, 1974. The single won the Juno Award for best-selling single of 1974.

The lyrics for the song tell of the singer meeting a "devil woman" and her 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.'

The guitar riff heard throughout the song's chorus is proportionate to the riff from Baba O'Riley by The Who. The riff follows a main pattern of A5, E5, then a D5, while the riff in Baba O'Riley is F5, C5, Bb5.

"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 indeed reminiscent of "My Generation." Randy insists that the song was performed as a joke for his brother, Gary, with no intention of sounding like "My Generation." Gary had a stutter, and Randy 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. 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.

But when winding up production for their third album, Charlie Fach of Mercury Records said the eight tracks they had lacked the "magic" that would make a hit single. Some band members asked Randy, "what about the work track?" Randy reluctantly mentioned that he had this ninth song, but didn't intend to use it on a record. He said, "We have this one song, but it's a joke. I'm laughing at the end. I sang it on the first take. It's sharp, it's flat, I'm stuttering to do this thing for my brother."

Fach asked to hear it, and they played the recording for him. Fach smiled and said "That's the track. It's got a brightness to it. It kind of floats a foot higher than the other songs when you listen to it."

Bachman agreed to include the song, but only if he could re-record the vocals first, without the stutter. Fach agreed, but Bachman says "I tried to sing it normal, but I sounded like Frank Sinatra. It didn't fit." Fach said to leave it as it was, with the stutter.

It is said that Gary Bachman has since lost his stutter.

The first single from the Not Fragilealbum was "Roll on Down the Highway." It performed well, but eventually stalled at #14 on the U.S. charts. "You Ain't Seen Nothing Yet," meanwhile, was becoming a hit as an album cut. Radio stations all over the USA were giving it a great deal of airplay. So much so, Bachman was embarrassed because he thought it was a stupid song, just something that he wrote as a joke.

Fach would regularly call him with airplay reports, asking for permission to release "You Ain't Seen Nothing Yet" as a single. Bachman says, "And I refused for three weeks... I was producer, so I had final say on what went out. I woke up one day and asked myself, 'Why am I stopping this? Some of my favorite records are really dumb things like 'Louie, Louie'... so I said to Charlie, 'O.K., release it. I bet it does nothing.'"

"You Ain't Seen Nothing Yet" debuted at #65 on September 21, 1974 and shot to the top of the Hot 100 seven weeks later. It was the only chart-topper for BTO. (While in The Guess Who, Randy had penned only one other chart-topper, "American Woman," which hit #1 in 1970.)

"You Ain't Seen Nothing Yet" also holds the record for falling farthest on the chart before returning to the Top 10. After falling to #34 two weeks after being in the #1 spot, it jumped back to #8 for two weeks, largely because of interest in the flip side, an instrumental called "Free Wheelin'".

On the UK version of the single, the label credits the band as " Bachmann–Turner Overdrive". It was kept off the top in the UK charts by "Lonely This Christmas" by Mud.

Bachman appears in the promo video for Bus Stop's 1998 remake of the song.

The song was always played at the end of the "Smashie and Nicey" sketch on the British sketch show, Harry Enfield's Television Programme.

The song was played in an episode of Ballykissangel.

It was also played on the third season premiere of Supernatural.

The song is featured in The Simpsonsepisode Saddlesore Galactica. At a BTO concert, Homer demands that they play the song one second after finishing it. When the band reminds him of this fact, he replies, "Whatever!"

A techno remix of the song was used as the theme song for ITV Sport's Formula One coverage from 2003 to 2005. The remix is by German group, The Disco Boys, titled "B-B-B-Baby."

The song is played at the beginning of the movie Studio 54 when the boys are going to club Studio 54 for the first time.

The song appears on the soundtrack of the film "Joe Dirt".

The song was, together with U2's "Beautiful Day", used as a theme song by the US Democratic Party following the US 2006 midterm elections.

During a trip to the US, Margaret Thatcher quoted the song when talking to an audience with Ronald Reagan. Telling the audience that "You ain't seen nothing yet". Appears in the CBC movie: Keep Your Head up kid: the Don Cherry Story, also shot in Winnipeg, Manitoba.