San Marzano tomatoes are a type of plum tomato grown in the Agro Sarnese-Nocerino region in Italy. Sometimes you’ll see tomatoes labeled as “San Marzano style” – this means they are the same variety of tomato but grown outside of the specific region in Italy. (Similar to how champagne can only be called that if it is produced in the Champagne region of France!) San Marzano (and San Marzano-style) tomatoes are perfect for using in spaghetti sauce because they are meaty and don’t have a lot of seeds, so they don’t add a lot of excess water content to the sauce.