The colour, but silent, film was recorded covertly at the concert in Kansas in 1964 and is believed to be the only recording of the 31 minute gig.
Fan Drew Dimmel, who is now selling the roll of 8mm film reel at a British auction house, was 15 when he went to see the band in his home city.
He took his father's brand new "movie" camera and despite strict restrictions about filming, managed to persuade a local reporter to take some shots.
After getting home, Drew checked the film contained footage of The Beatles then shut it in a drawer and forgot about it.
Two months ago the 59-year-old was clearing out his parents' home and was stunned when he discovered the tape still in its photo-lab box.
Although there are just two minutes of footage the pre-sale estimate is a whopping 6,000 pounds and Beatles collectors from around the world are expected to bid.
The gig at the Municipal Stadium in Kansas was controversial because of the unpopularity of Charles Finley, owner of the Kansas City Athletics Baseball Team.
The local press urged a boycott of the concert in protest against Finley and as a result the stadium was almost half empty.
The Beatles' manager Brian Epstein had managed to negotiate a fee of $150,000 for the gig, which helped leave Finley out of pocket.
Mr Dimmel said: "When confirmation was announced on my local "rock" station, WHB, that tickets were going on sale to see The Beatles, live, at Municipal Stadium in Kansas City I persuaded my dad to drive me down to the ticket booth.
"I bought two field-level tickets, paying $6.50 apiece; one for my little brother and one for me. I was 15 and he was 12.
"On the evening of September 17, 1964, 20,000 of us gathered at Municipal Stadium to hear The Beatles.
"My father agreed to lend me his brand new "colour" regular-8mm movie camera for the evening.
"I was going to stand in front of the stage and film the show but, when the lights dimmed a policemen told us to find our seats.
"A local reporter who was a friend of my dad was in the press barrier and he recognised us and said he would try and get some shots of The Beatles for us.
"I thanked him and obediently handed my dad's brand new movie camera to a total stranger.
"The next day I took the film to our local camera store, making no mention of its contents, and waited for them to develop it. I paid four dollars developing fee.
"I went straight home, checked to see that images on the little reel were The Beatles, opened the drawer of our old desk and placed it in the bottom of the drawer.
"And there it's been for the last half of a century until we cleared out my parent's estate two months ago.
The sale will be held on November 4.