Thunder in the Glens is an annual motorcycle rally held in Aviemore, Scotland and, although originally for Harley-Davidson(R) bikes, for many years the event has been open to all varieties of bikes.  Thunder is run by the Dunedin Chapter of the Harley Owners Group(R) and is now the largest event of its type in Europe.

The rally was created in 1996 by Bob Watson, a founding member of Dunedin HOG.    This followed the first significant Dunedin rally which was also organised by Bob in Pitlochry, Scotland; the "Faskally Rally".