Eaton Vance Senior Income Trust is a United States-based diversified, closed-end management investment company. Its investment objective is to provide a high level of current income consistent with the preservation of capital, by investing in senior, secured floating-rate loans. The trust invests in below-investment-grade floating-rate loans, which are considered speculative because of the credit risk of their issuers. Its portfolio of investment consists of aerospace and defense, automotive, beverage, building and development, business equipment and services, cable and satellite television, and other areas.