[File:Barber on the sidewalk of a street in Nishapur 4.JPG|thumb|350px|'Suppose you walk past a barber's shop one day, and see a sign that says:
"Do you shave yourself?
If not, please come in and I'll shave you!
I shave anyone who does not shave himself,
and no one else".
So the question is: "Who shaves the barber?"'
—the barber paradox|alt=Fixing quotation marks]]A mathematical problem is a problem that is amenable to being represented, analyzed, and possibly solved, with the methods of mathematics. This can be a real-world problem, such as computing the orbits of the planets in the solar system, or a problem of a more abstract nature, such as Hilbert's problems.
It can also be a problem referring to the nature of mathematics itself, such as Russell's Paradox.