Lannoy is a commune in the Nord department in northern France. With a land area of only 0.18 km², it is the third-smallest French commune b…Lannoy is a commune in the Nord department in northern France. With a land area of only 0.18 km², it is the third-smallest French commune by surface area. It also has the highest density of population of any commune outside of the Île-de-France region, slightly greater than that of the city of Lyon.