An open problem is a known problem with importance or interest in some scientific area, that can be accurately stated, and has not yet been solved (no solution for it is known). Notable examples of for-long open problems in Mathematics, that have been solved and closed by researchers in the late twentieth century, are Fermat's last theorem and the Four color theorem. Important open problems exist in many fields, such as theoretical computer science, physics and mathematics.

It is common in graduate schools to point out open problems to students. Graduate students as well as faculty members often engage in research to solve such problems.

See also

• List of unsolved problems