Siacoin [SC] is the native utility token of Sia, a blockchain-based distributed, decentralized cloud storage platform. Sia acts as a secure, trustless marketplace for cloud storage in which users can lease access to their unused storage space. Agreements and transactions are enforced with smart contracts, and Siacoin is the medium of exchange for paying for storage on the network. The main goal of the project is to become the "backbone storage layer of the internet."
Sia was originally announced in May 2014 before being revised and re-announced a year later in May 2015. It officially launched in June 2015.