This week Billboard Magazine came out with the 100 best boy band songs.  Of course there were the ones that you would expect like Backstreet Boys, NSync, BIg Time Rush and others like that.  But there were also mentions of the Monkees, the Jackson 5 and... the Beatles.

This is what Wikipedia says about what criteria makes up a boy band...

The Liverpool quartet known as The Beatles were not only the quintessential rockband, but many considered John Lennon, Paul McCartney, George Harrison and Ringo Star to be the original boy band -- especially in the early 1960s when young girls would scream at the top of their lungs and pass out upon first sight...https://en.wikipedia.org/wiki/Boy_band

Hulton Archive, Getty Images

So, you have 4 20ish boys, with screaming girls, and they sing love songs.  As much as most people, especially Beatles fans won't want to admit that they were a boy band, and in the same category as the Backstreet Boys or New Kids on the Block, for that time...they were the original boy band.