The Seridahn River was a significant river located in the South March Lands of the Republic of Siddarmark.

It began in the Snake Mountains, flowing southwards, meeting with the East Seridahn River near the settlement of Riverfork, further on with the St. Alyk River, near Trevyr, and finally emptying into Thesmar Bay, near the city of Thesmar. (map)

During the civil war, the Seridahn River region was heavily contested between the loyal factions of Republic of Siddarmark Army, and the Royal Dohlaran Army, and later the Imperial Charisian Army. (MTAT)