Interest Protocol is a fractional reserve banking protocol on the Ethereum blockchain that pays interest to all depositors. Interest Protocol issues a stablecoin, named USDi, that is both over-collateralized and highly scalable. USDi holders automatically earn yield without having to stake, which means Interest Protocol provides yield opportunities to gas-conscious users. Compared to lending protocols without fractional reserves, Interest Protocol can generate more loans from a given amount of capital while incurring less liquidity risk.