The Oberalpstock or Piz Tgietschen is a mountain in the Glarus Alps between the cantons of Uri and Graubünden. Its massif separates the valleys of Maderanertal (Uri) and Surselva near Sedrun (Graubündnen).

The Oberalpstock is the highest summit of the Glarus Alps west of the Tödi , and also the highest mountain in the Canton of Uri east of the Reuss.