One trail runner just wrapped the wildest marathon of his life ... and the finish line came courtesy of Donald Trump , who swooped in with a surprise presidential pardon after a record Grand Teton trail run somehow morphed into a federal fiasco.

Michelino Sunseri hopped on TMZ Live Thursday and reflected on the saga ... telling us how he was taking on a Grand Teton trail in Wyoming last year -- a historic path that’s been around since the '30s, leading to the 13,775-foot-high peak -- in an attempt to break the speed record ... when one switchback somehow turned him into Public Enemy No. 1, with record-keepers tattling to the feds. Gallery Launch Gallery Getty

Catch the clip, ’cause Michelino lays out the absurdity ... describing how there were more than 20 feds, some decked o

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