The Intermunicipal Cup 3H MTB Endurance is a mountain bike endurance race series held across six events in various municipalities including Alenquer, Loures, Mafra, Oeiras, Amadora, and Lisbon. The 2026 edition welcomes participants aged 5 and above, with categories for juniors, adults, masters, and e-bikes.

The races take place on circuits approximately 4 to 7 km long for the 3-hour endurance events and 1 to 3 km for juvenile races, with specific shorter distances for younger categories. The competition is open to both licensed competitive athletes and non-federated riders, fostering an inclusive amateur competitive atmosphere.

Alongside the endurance races, juvenile MTB races are held on the same days, providing a comprehensive event for all ages. The series awards points and prizes across categories, culminating in a final trophy ceremony recognizing top performers.