"My Last Duchess" is a dramatic monologue in 28 heroic couplets by the Victorian poet Robert Browning (1812-1889). Browning was particularly renowned for dramatic verse.
In the poem, the speaker, an Italian duke, describes a portrait of his last wife, whom he may or may not have had murdered. His audience is there to negotiate a new marriage for the duke. (Wikipedia summary here.)
This poem is almost guaranteed to appear on the GRE Literature test--read it multiple times. Know the famous lines below by heart:
-"She had a heart--how shall I say?--too soon made glad"
-"I gave commands; then all smiles stopped together"