Tønder Festival is an annual folk music festival that has been held in the Danish town of Tønder, located in the municipality of the same name, since 1975.

In June 1974, a group of young music lovers organized a small three-day festival of folk music, ballads and beer in an old mill on the banks of the Vida River to celebrate the day of the summer solstice. The event proved to be a success and the boys held another festival in September. Interestingly, both times the speakers included Scotsman Rob Sinclair, who later became one of the regular organizers.

The first official folk music festival in Tonnerre was held in August 1975. The end of August was chosen for several reasons. First, there were other folk festivals taking place in Denmark at the time: in June in Skagen, and in July in Roskill. The festival in Tønner did not overlap with any of them and closed the summer festival calendar. Secondly, there is a fairly high probability of good weather in Denmark in August. The musical program of the debut festival was quite eclectic, ranging from a military band to psychedelic rock bands.

Over the years, the Tønner Festival has become one of the most important festivals of traditional and contemporary folk music not only in Denmark, but also in the whole of Europe. The festival features musicians from Scandinavia, Ireland, Scotland, England, the Netherlands, Canada, the USA and other countries. The genres represented in its program range from Irish and Scottish folk to Scandinavian and Baltic folk music.

Concerts are usually held in 9-10 venues within the city and in large tents directly in the festival area. Most concerts are seated, but some have both seating and standing room. Initially it was not possible to buy a single ticket for all concerts because the venues varied in capacity, but in recent years the festival did switch to a wristband pass system standard for many music festivals.