Pelasgiotis (Ancient Greek: Πελασγιῶτις, romanized: Pelasgiōtis) was an elongated district of ancient Thessaly, extending from the Vale of Tempe in the north to the city of Pherae in the south. The Pelasgiotis included the following localities: Argos Pelasgikon, Argyra, Armenium, Atrax, Crannon, Cynoscephalae, Elateia, Gyrton, Mopsion, Larissa, Kondaia, Onchestos river and town, Phayttos, Pherae, Scotussa, and Sykourion. The demonym of the district's inhabitants is Pelasgiotae or Pelasgiotes (Πελασγιῶται, Pelasgiōtai).
Along with Achaea Phthiotis, Thessaliotis and Histiaeotis, the Pelasgiotis comprised the Thessalian tetrarchy, governed by a tagus, when occasion required.