Final answer:
Marseille, the largest port on the Gulf of Lion, is located in France. It is a significant Mediterranean port city and a crucial economic hub for the country.
Step-by-step explanation:
The country that has Marseille, its largest port on the Gulf of Lion, is France. Marseille is an important Mediterranean port city and is known as one of the main gateways to the Maghreb region which includes countries like Algeria, Libya, and Morocco. Although other countries such as Algeria, Libya, and Morocco have significant port cities along the Mediterranean coast and have considerable areas of desert conditions, Marseille is specifically located in France and serves as a crucial economic hub for the country and the wider European region.