What region is San Marzano in?

Excuse me, could you please clarify for me which region San Marzano is located in? I'm trying to get a better understanding of its geographical location and I'm having a bit of trouble pinpointing it on the map. Is it perhaps nestled within the rolling hills of Tuscany, or perhaps nestled in the picturesque countryside of another Italian region? I'd greatly appreciate your assistance in clarifying this matter.