Mahasiva was a king of the Anuradhapura Kingdom who reigned for ten years. He was another son of King Mutasiva and ascended the throne after his brother Uttiya. Like his brothers who reigned before him, Mahasiva was a pious king. According to the chronicles, he was a great supporter of the monk Bhaddasala, for whom he built the Bhaddasala temple in Anuradhapura. His reign is noted for its stability and continuation of the royal family's patronage of Buddhism. He was succeeded by his younger brother, Suratissa.

King Mahasiva