The city is located in the territory of the Altomilanese, at the intersection of the provinces of Milan, Como, Varese and Monza and Brianza, without being closely linked to any of the provincial capitals in particular. A considerable part of the population gravitates, for work or study reasons, on Milan, but the city also enjoys a life of its own, in which the inhabitants of neighboring municipalities also participate (Gerenzano, Turate, Uboldo, Rovello Porro, Origgio, Caronno Pertusella , Solaro, Rovellasca, Ceriano Laghetto), who attend local schools or work in the city.
Saronno is crossed by the Lura stream, which is born in the territory of the Municipality of Bizzarone and flows into the Olona area just outside Milan. The stretch of torrent included in the city territory is largely underground. Part of the municipal territory is included in the boundaries of the Parco del Lura.
The earliest documentary evidence of the existence of Saronno is a notarial paper of 796, concerning a loan as a pledge contracted by that Johannes de Vico Salomno filius quondam Aretheo qui fuit notarius, who obtains from a certain Erminaldo the sum of ninety deniers. silver, pledging all his existing assets in Vico Solomno.
Before arriving at the definitive name of Saronno, over the centuries the city has taken various names found through historiographical documentation. In order of time, Saronno is mentioned as Solomno (year 903), Serogno (year 1150), Sorogno (XII century), Serono (XIII century) and soon after Sarono.
These name changes derive from a phenomenon that is found with great frequency in the Lombard dialects to the west of the Adda, including the Saronic dialect: the rotacism, or the change of the / l /, especially if intervocalic, in / r / , indicated by the linguist Clemente Merlo as one of the most characteristic effects of the deep and ancient Ligurian substratum.
In medieval times, Saronno was part of the Contado del Seprio and therefore of the Duchy of Milan. Among the news of this time, we know that Cecilia Gallerani (famous as the subject of the painting Dama with the ermine of Leonardo da Vinci) obtained as a gift from the Duke Ludovico il Moro the income of the Saronese territory.