Yes, Pizza Is Served Unsliced In Italy. Here's Why.
If you find yourself ordering a pizza at most restaurants in Italy, don't expect to receive it already sliced. Typically, you'll receive a perfectly intact, unsliced pie. There's a few reasons for this: On the culinary side, ingredients for a margherita pizza, like Italian mozzarella and juicy San Marzano tomatoes, tend to have a fairly high liquid content, so this leaches out when it's cooked. If the pizza was sliced, this liquid would seep out under the pizza and soak the edges of the crust — not ideal. Italian pizzas typically have a fairly thin base, which doesn't help with all that liquid.
Pizza tastes so good in Italy and it's usually meant to be eaten fresh from the oven — slicing it exposes more surface area to the air, potentially cooling it down faster, putting a dent in that freshness. Italians tend to order a single pizza just for themselves, making slicing less necessary as it doesn't need to be shared. Finally, some Italians suggest that unsliced pizzas are more aesthetically pleasing.
Where you can get sliced pizza
Some Italians argue that sliced food is meant primarily for a fast food context, not the more formal setting of a restaurant. However, this means that it's still possible to find sliced pizza in Italy if you go to the right place, although you won't exactly get a New York style slice of pizza. Pizza al taglio refers to pizza that's made as a large square or rectangle and served as slices. It's typically cut in front of you with customers indicating the size of the slice they want, paying based on the weight of the slice. Pizza al taglio is particularly common in Rome, where it's usually served in casual, grab-and-go type restaurants.
As for those unsliced pizzas, one final issue is the question of how you're meant to eat them. Generally, Italians will eat a restaurant pizza with a knife and fork, which fits in with the general cultural tendency to not share them. Those who forgo the knife and fork may need to fold the pizza to hold the liquid in, and this can be difficult when a pizza is served piping hot. If this is your preference, you'll probably be expected to slice it yourself — restaurants will usually do it if you ask, but it's seen as more of a thing that's done for kids and elderly people.