Femsjøen rundt is a 100 km road cycling race held in Halden, Norway. It begins and ends at Tistedalen skianlegg and takes place in autumn. The race is open to participants aged 17 and older, with categories and start groups determined by age. A non-timed recreational class is also available for those who prefer to ride the course without competing against the clock. Riders anticipating a finish time exceeding four and a half hours are advised to select this option.
The course encircles the Femsjøen area and is predominantly flat, allowing for a fast pace. However, it does feature significant climbs. Linnekleppen, the highest point in Østfold, is located along the route. The final kilometre ascends sharply to the finish line, offering a challenging uphill sprint for competitive cyclists. The race has been a fixture in Halden's cycling scene since the early 1980s. In addition to the standard mass start, a team competition is held for groups of up to 10 riders.