Apatsahayesvarar Temple, Alangudi or Guru Sthalam or Tiru Irum Poolai is a Hindu temple dedicated to Lord Shiva located in the village of Alangudi in the Valangaiman taluk of Tiruvarur district, Tamil Nadu, India. It is one of the Navagraha(nine planets) temples situated in the Cauvery delta. It is one of the 275 Paadal Petra Sthalams, where Campantar, one of the four most revered Nayanars (Saivite Saints) have sung the glories of this temple.
The temple has a 5-tier rajagopuram surrounded by two prakarams(closed precincts of a temple.
Legend is that Siva consumed deadly poison, giving rise to the name Alangudi and deity being termed Apatsahayesvarar, indicating saviour during hard times.
The temple is one of the nine Navagraha sthalas(Temples of Nine planets) located in the Cauvery Delta region dedicated to planet Jupiter, called Dakshinamoorthy, the Guru.