Solitude is a state of seclusion or isolation, i.e., lack of contact with people. It may stem from bad relationships, deliberate choice, infectious disease, mental disorders, neurological disorders or circumstances of employment or situation (see castaway).

Short-term solitude is often valued as a time when one may work, think or rest without being disturbed. It may be desired for the sake of privacy.

A distinction has been made between solitude and loneliness. In this sense solitude is positive.