The Sellaronda is a ski and road circuit around the Sella Massif, a group of mountains in the Dolomites which lies between the valleys of Fassa, Livinallongo, Badia and Gardena, and includes ski lifts to complete the circuit in summer and in winter. It also includes numerous cycle routes, with the asphalt road circuit and cross country routes.

The Sellaronda is known as the 4 Pass Circuit, as it crosses four Alpine cols linking as many valleys of the Dolomites:

Sella Pass (2240 m)
which connects Val di Fassa with Val Gardena
Pordoi Pass (2239 m)
which connects Val di Fassa with Livinallongo del Col di Lana
Campolongo Pass (1875 m)
which connects Livinallongo del Col di Lana with Val Badia
Gardena Pass (2121 m)
which connects Val Badia with Val Gardena. The Sellaronda touches three provinces and two regions: the autonomous province of Bolzano in Trentino-Alto Adige and the province of Belluno in Veneto.
You can ski round the Sellaronda circuit in winter without ever removing your skis, thanks to the ski lifts, shortcuts and ski runs which connect it completely. You can do the circuit in both directions (clockwise and anti-clockwise) and start it from almost any of the resorts around the Sella Massif. The total circuit, including ski lifts and runs is approximately 40 km long and also includes the more technical runs, such as the "Arabba – Porta Vescovo" or the "Lupo Bianco" run at Canazei. The Sellaronda is part of one of the largest, most important and most famous ski areas in the world: the Dolomiti Superski.

The Sellaronda can also be covered in summer both clockwise and anti-clockwise on foot. It is not such a challenging route of about 5-8 hours, although you do need to be reasonably fit. As in winter, the ski lifts and the Sellaronda bus are there to help you.
The road across the four passes is approximately 55 km long and is used by cyclists in particular. The Giro d'Italia has passed up these steep climbs many a time.

The now very famous Maratona dles Dolomites - Enel starts from the Sella circuit. It is held every year between the end of June and the beginning of July.

Since 2006, an amateur, non-competitive event called the Sella Ronda Bike Day has been held, during which the four passes are closed to traffic and reserved for a single day for bicycle enthusiasts.