John Travolta's new signature beret look isn't some random fashion phase ... he says it's actually the result of a years-long mission to reinvent himself.

The actor opened up to Variety about the head-turning accessory that's grabbed attention around the world ... revealing he intentionally adopted the look after getting bored with seeing the same version of himself in photos year after year.

Hear him out ... John says he looked back at old pictures and realized he could barely tell one era from another. So, he started researching legendary filmmakers and noticed a common theme ... many of the old-school directors he admired wore berets and glasses ... embracing an artistic style tracing back centuries.

The look clearly caught on ... John says he's purchased about a dozen berets ... so don't him to switch up his look any time soon.

John even joked he may need to launch his own line after landing on several best-dressed lists ... arguing men don't have nearly enough fashion options and should have more fun experimenting with their style.

Listen to what inspired the "Grease" star's eye for style back in the '60s ... turns out, he's been playing fashion consultant for years!!!