William Greenleaf Eliot (August 5, 1811[1] – January 23, 1887[2]) was an American educator, Unitarian minister, and civic leader in Missouri.

Eliot was active in civic life and was instrumental in founding many civic institutions, including the St. Louis Public Schools, the Saint Louis Art Museum, Mission Free School, South Side Day Nursery, and the Western Sanitary Commission to provide medical care and supplies during the Civil War.

In 1861, he was part of a small group of men who helped Generals Nathaniel Lyon and Francis P. Blair to retain Missouri in the Union.

When Ralph Waldo Emerson visited St. Louis, he met Eliot and called him "the Saint of the West.

In 1853, he co-founded Washington University in St. Louis, initially called Eliot Seminary to his chagrin.

In 1859 he founded Mary Institute, a school for girls which he named after his daughter, who died young.

These ranged from works of theology in the Unitarian tradition to specific moral advice to young people.