Saint Isaac the Syrian (613 - 700 AD) was a Christian bishop in the Syrian Church of the East and theologian best remembered for his written works on Christian asceticism. He is regarded as a saint in almost all Orthodox churches.

St. Isaac is remembered for his homilies on the interior life, which are favorite among Christian monks. They survive in Syriac manuscripts and in later Greek, Arabic, and Georgian translations.

Isaac's writings offer an example of ascetical texts written by an experienced hermit and is thus an important author when it comes to understanding early Christian asceticism. Many of his writings are included in the Philokalia.