Sirmione is situated along the homonymous peninsula that juts out into Lake Garda for about four kilometers and divides into two parts, the southern lake shore. Part of the municipal territory extends to the east of the peninsula to include that of Punta Grò.
The hinterland extends in the direction of the moraine hills that surround the southern part of the lake and includes parts of the production area of Lugana.
The town is bordered to the south-east Peschiera del Garda and south-west with Desenzano del Garda. The section of the lake is bordered on the east by Lazise and Peschiera del Garda and north with Padenghe sul Garda.