Sesiwn Fawr Dolgellau is a world music event held in the town of Dolgellau in Wales. The event was established in 1992, and was held in the town's streets. Since 2002, Sesiwn Fawr Dolgellau has been held on the Marian, a large grassy area next to Afon Wnion. There is a campsite provided for visitors. As with a number of Welsh festivals, there was no Sesiwn Fawr in 2009, partly due to financial reasons resulting from poor ticket sales in previous years and also as the 2009 National Eisteddfod was taking place in nearby Bala.
However, in 2011, Sesiwn Fawr returned to the festival calendar although on a smaller scale than the 2002–08 Sesiwn Fawr era. The organisers decided to return to the festival's original roots by introducing a primarily folky line-up which included Mynediad am Ddim, Cowbois Rhos Botwnnog, Calan and Steve Eaves. The 2011 Sesiwn Fawr also included a twmpath dawns (a large communal folk dance) on the town's Eldon Square on the following Saturday. After receiving positive reviews, organisers decided to follow a similar format again for 2012.
In the past, the line-up has included Super Furry Animals, Steve Earle, The Dubliners Iwcs a Doyle, Burning Spear, Bob Geldof, Saw Doctors, Bryn Fôn, Meic Stevens, Geraint Jarman a'r Cynghaneddwyr, Derwyddon Dr Gonzo, Grupo Fantasma, Paul Dooley, N'Faly Kouyate, Endaf Emlyn, Cerys Matthews and Goldie Lookin Chain.