Apollonius of Perga or Perge (c. 262 BC - c. 190 BC) was a Greek geometer and astronomer, noted for his writings on conic sections. It was Apollonius who gave the ellipse, the parabola, and the hyperbola the names by which we know them. The hypotheses of eccentric orbits, or equivalently, deferent and epicycles, to explain the apparent motion of the planets and the varying speed of the Moon, are also attributed to him.

Only two of his works survive:

• Cutting-of a Ratio (two books preserved in an Arabic translation)
• Conics (four books preserved in the original Greek, three in Arabic and one lost).

His innovative methodology and terminology, especially in the field of conics, influenced many later scholars including Ptolemy, Isaac Newton and René Descartes.

See also

• Descartes' theorem