The Italian city considered the birthplace of modern pizza is Naples. Pizza-like flatbreads existed in many ancient cultures, but the modern dish developed in Naples, where topped breads became an important food for working people.
Between the 16th and 18th centuries, Neapolitan cooks used inexpensive flatbreads with ingredients such as garlic, salt, oil, cheese, and later tomatoes. Tomatoes came to Europe from the Americas after the Columbian Exchange and were initially viewed with suspicion, but they eventually became central to the style of pizza associated with Naples.
The city’s street vendors and early pizzerias helped establish pizza as a recognizable dish. Antica Pizzeria Port’Alba, first established as a stand in 1738 and opened as a restaurant in 1830, is widely regarded as one of the world’s oldest pizzerias.
Pizza’s exact ancient ancestry is broader than Naples, so “birthplace” refers to modern pizza rather than every earlier topped flatbread. Florence, Milan, and Rome each have important food traditions, but Naples is the canonical answer.