Sant Celoni is a municipality located in the Vallès Oriental comarca within the Catalonia region of Spain. The town is situated in the valley of the Tordera river, positioned between the Montseny and Montnegre mountain ranges. The primary portion of the settlement is located on the left bank of the river.
The municipality currently encompasses the territory of the former municipalities of Montnegre and Olzinelles. As a result of these combined territories, Sant Celoni possesses the largest area within its comarca. The region is accessible via the AP-7 Motorway, the C-251 road, and a Renfe railway station situated on the line connecting Barcelona and Girona.