Ralph Lauren Had Oprah On The Brain and Ran Me Over ... NEW LAWSUIT

Preppy Ralph Lauren should stick to yachting ... because his driving sucks ... according to a new lawsuit.

Ralph invited Oprah to his opulent, well-decorated Colorado Double RL Ranch back in 2011. One of them had a bright idea -- doing an interview in his vintage 1948 Jeep ... which we're guessing smelled like perfumed potpourri.

A guy who was outfitting the whip with microphones was working near the back bumper when Ralph took the wheel and suddenly shifted into reverse ... violently striking him -- at least that's what he alleges in a new lawsuit.

The dude -- who worked for Harpo -- says he suffered injuries to his head, body and limbs, muscles, tissues, nerves and blood vessels in his head. He wants more than $50k to cover his troubles and is suing both Ralph and Harpo.