Trysil is a municipality in Hedmark county, Norway. It is part of the traditional region of Østerdalen. The administrative centre of the municipality is the village of Innbygda. The municipality of Trysil was established on 1 January 1838 (see formannskapsdistrikt).
The municipality (originally the parish) is probably named after an old farm - and this was most likely the original name of Prestgarden ("the vicarage"), where the first church was built. The meaning of the first element is unknown (maybe an old river name), the last element is sil which means "quiet stretch of a river". Prior to 1906, the name was spelled "Tryssil".
The coat-of-arms is from modern times. They were granted on 21 October 1991. The arms show two silver Ski poles on a blue background. It is meant to symbolize Trysil in the past, present, and future. It was designed by Bjørn Ellefsæter.