Siapiccia is a comune, or municipality, located in the Province of Oristano within the Italian region of Sardinia. It is situated approximately 90 kilometres (56 mi) northwest of Cagliari and about 15 kilometres (9 mi) east of Oristano.
As of December 31, 2004, the municipality covered an area of 17.9 square kilometres (6.9 mi2) with a recorded population of 365 residents.