Altarnun is a village and civil parish in Cornwall, England, United Kingdom.
It is located on the north-eastern edge of Bodmin Moor at grid reference SX 223 811.
The parish of Altarnun includes the village of Fivelanes and the hamlets of Bolventor, Treween and Trewint, and had a population of 976 according to the 2001 census.
This increased to 1,084 according to the 2011 census.
Other hamlets in the parish are Bowithick, Palmersbridge, South Carne, Tolborough, Lower Tregunnon, and Tredaule.
The area of the parish is 15,018 acres, the largest in Cornwall.
By the time of the 2011 census the figures for the ward of Altarnun were provided.
This ward contained 48 locations in the area and gave a population of 4,038.