The frozen pizza brand that introduced the slogan “It's not delivery, it's DiGiorno” is DiGiorno.
DiGiorno is an American frozen-pizza brand owned by Nestlé. The tagline was designed to suggest that the pizza’s quality and freshly baked appearance could make it seem like a delivered restaurant pizza. The slogan became one of the brand’s most recognizable marketing lines.
The DiGiorno product line began in 1991, while its pizzas became available in the United States in 1995. The brand was previously part of Kraft’s frozen-pizza business; Nestlé acquired that business in 2010. In Canada, the same products were sold under the Delissio name, so the tagline there referred to Delissio rather than DiGiorno.
A common mix-up is confusing DiGiorno with delivery-focused chains such as Domino’s or Pizza Hut. DiGiorno is a supermarket frozen-food brand, and its slogan is specifically a contrast between frozen pizza and restaurant delivery.