Spearthrower Owl or Atlatl Cauac was the emperor of Teotihuacan at the start of height of its influence across Mesoamerica in the 4th and 5th century. He assended to the throne on 4 May, 374 (already an adult at the time), and the long lived ruler died on 9 June, 439.

As no surviving Teotihuacan historical records survive, he is only known from references in the incriptions of the Maya civilization heiroglyphs.

Under his rule Teotihuacan armies subjected much of the central Maya area to client states. His general Siyah K'ak' conquered the Peten. One of his sons, Nun Yax Ayin, was installed as king of Tikal in 379. One of his brothers, Smoking Frog, was installed as king of Uaxactun. Later Maya rulers were still mentioning their decent from the illustrious Spearthrower Owl on monuments 5 generations later.

In addition to Tikal and Uaxactun, Spearthrower Owl is mentioned in texts at other sites, including Yaxchilan and Tonina.