Robert Silliman Hillyer (June 3, 1895 – December 24, 1961) was an American poet.
Hillyer was born in East Orange, New Jersey. He attended Kent School in Kent, Connecticut, 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. He had long links to Harvard University, including holding a position as a Professor of English.
From 1948 to 1951 Hillyer worked as a visiting professor at the Gambier Institution at Kenyon College and from there went to serve on the faculty at the University of Delaware.
While teaching at Trinity College in Hartford, Connecticut in the late 1920s, Hillyer was made a member of the Epsilon chapter of the prestigious St. Anthony Hall Delta Psi literary fraternity in 1927.
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".
American composer Ned Rorem's most famous art song is a setting of Hillyer's "Early in the Morning".
Hillyer is remembered as a kind of villain by Ezra Pound scholars, who associate him with his 1949 attacks on The Pisan Cantos in the Saturday Review of Literature which sparked the Bollingen Controversy.