Sennariolo is a comune, or municipality, located in the Province of Oristano on the island of Sardinia, Italy. It is situated approximately 35 kilometres (22 mi) north of Oristano and about 120 kilometres (75 mi) northwest of Cagliari.
The municipality covers a total area of 15.7 square kilometres (6.1 mi2). As of December 31, 2004, the population of Sennariolo was recorded at 185 residents.