Theme in literary terms, refers to a recurrent idea or topic in writing. It is often also the main subject of such writing. In most instances, though, a literary work explores various themes, as does Browning's poem.

The most obvious theme in this monologue is possession. It becomes apparent from the outset that the Duke derives much pleasure from his belongings. He speaks about "my" last Duchess, as if she were an object. He takes pride in talking about the painting he had commissioned. It gives him great joy that the artist, Fra Pandolf, could so accurately depict his previous wife's image on canvas. On a sinister note, though, he comments about the fact that his wife was apparently affected by the artist's complimentary remarks during the sitting.

Such stuff
Was courtesy, she thought, and cause enough
For calling up that spot of joy.

"My Last Duchess" by Robert Browning uses the form of the dramatic monologue to illustrate major themes typical of Browning's work.

The first major theme is that of the collector, a theme also found in "The Bishop Orders his Tomb." This theme illustrates a way people react to art by collecting it as a status symbol rather than appreciating its intrinsic worth. The Duke who narrates "My Last Duchess" is a collector in his attitude towards people (especially women) as well as objects. We see the relationship between them in the discussion of the portrait of the Duchess. The Duke says:

I gave commands;
Then all smiles stopped together. There she stands
As if alive.

The duchess has been transformed into an object similar to the statue of Neptune.

Another major theme is hypocrisy and the way in which a convention surface can mask evil.