Frisian (alternate spelling: Friesian) can refer to:

• An inhabitant of Frisia (consisting of the province of Friesland in the Netherlands, and portions of the states of Lower Saxony and Schleswig-Holstein in Germany), see Frisians.
• The ancient tribe of Frisians inhabiting Friesland.
• The Frisian language, which itself is divided into three languages:
  • West Frisian language, spoken in the Netherlands;
  • East Frisian language, spoken in Lower Saxony, Germany; and
  • North Frisian language, spoken in Schleswig-Holstein, Germany.
• The Old Frisian language.
• A breed of horse from Frisia, see Friesian horse.
• A breed of cow, see Holstein Friesian.
• A school of philosophy based on the works of Jakob Fries.

Frison