Jodar was ranked outside the top 900 a year ago but will climb to 57th in the world on Monday, having only turned professional in December after two seasons of US college tennis.
"It's incredible. I have no words, honestly, to describe this feeling right now," said Jodar.
"I'm super happy that I could get the title here in Marrakesh. The first time for me in Marrakesh and Morocco. I loved the crowd, everyone who came to support me and watch the final."
Jodar adds his name to an elite list of Spaniards to win a tour-level title before turning 20, joining Rafael Nadal, Carlos Alcaraz, Carlos Moya, Juan Carlos Ferrero and Tommy Robredo.
Trungelliti, 36, was the oldest first-time ATP finalist in the Open era. He will become the oldest debutant in the men's top 100 since 45-year-old Dane Torben Ulrich in 1973. Trungelliti will rise to a career best of 73rd on Monday.