The title of the poem is derived from the first sentence uttered by the Duke who is showing the painting to an important visitor. His way of describing his late wife characterizes him as egocentric, and this self-characterization continues throughout the entire monologue. The phrase "My last Duchess" is somewhat ambiguous because it suggests that his former wife was not his first wife but that he might have had one or more wives before her. It also suggests a complete lack of feeling for the last wife as a human being, which is what is so chilling about this entire dramatic monologue. If he cared anything about her he would have said, "That's my first wife" or "That's my late wife" or something else with at least a hint of love and bereavement. The painting is not his wife but just a representation of his wife, but he doesn't seem to distinguish between a picture and a living human being whom he unconsciously describes as a warm, gentle, sensitive, charming woman. The phrase "My last Duchess" also implies that he is more concerned about his "next" duchess, the young woman he has set his sights on because she will bring him a big dowry. It seems truly cold and insensitive on his part to show his visitor a painting of the wife he has just had murdered when the silent visitor is there to discuss marriage arrangements with the Duke's intended bride.
The visitor must become shocked or disgusted, because it appears that he stands up abruptly and starts to leave the room without a word of explanation or apology. The Duke says, "Will't please you rise?" Then it appears that the visitor has turned his back and is going to walk downstairs alone. The Duke says, "Nay, we'll go / Together down, sir." We can only imagine what the visitor will report to the Count who is the intended bride's father. Hopefully, he might advise him to break off the engagement and spare the poor girl a fate similar to that of the Duke's "last Duchess."