San Martin Txiki ("Little Saint Martin") is the trickster figure from Basque mythology. Txiki (pronounced "cheeky" [ˈt͡ʃiːki]) means "little" in an affectionate sense. San Martin Txiki is often called simply Martintxiki or Samartitxiki. He stole the secrets of planting, sowing, and harvesting from the Basajaunak (lords of the woods). He also invented the first saws, modeling them after the edges of the chestnut leaf.

San Martin Txiki also exists in Aragonese mythology in the valleys of Tena, Ansó and Broto (places where local toponymy derives from Basque) under the name San Martinico.