Robert Silliman Hillyer (1895–1965) was a poet and academic, becoming Professor of English at Harvard University.

He was born in East Orange, New Jersey and graduated from Harvard in 1917 after which he went to France and volunteered with the S.S.U. 60 of the Norton-Harjes Ambulance Corps serving the Allied Forces in World War I.

His work is in meter and often rhyme. He is known for his sonnets and for such poems as "Theme and Variations" (on his war experiences) and the light "Letter to Robert Frost". The Collected Verse of Robert Hillyer (1934) won the Pulitzer Prize for Poetry in that year. Other works include The Coming Forth by Day: An Anthology of Poems from the Egyptian Book of the Dead (1923), the novel Riverhead (1932), and In Pursuit of Poetry.

Hillyer was identified with the Harvard Aesthetes grouping.