Don McLean's Still Got It at 72 with Playboy Model Girlfriend

Don McLean's playing a young man's game, and dominating so hard ... he's already got a trophy.

The legendary "American Pie" singer was leaving a hotel Wednesday in London with his much younger, and total smoke show of a Playboy model girlfriend ... Paris Dylan.

We'll do the math -- she's 24, he's 72, which adds up to ... get it, Donnie!

He was dressed age-appropriately for an oldie, but goodie folk singer. Paris also appropriately rocked a curve-hugging dress. Even though she's posted pics with a shiny rock on her finger, Don's people have told us their thing is strictly professional.