The term 'dissident' got well-known in the 20th Century in connection with opponents of the regime in the Soviet-Union and its satellite states, and in communist China, but it seems likely that any political régime or religious belief has its dissidents, both internally and externally.

Consequently, it is difficult to say much about dissidents in general, except this: Wherever it is dangerous to differ in opinion from the powers that be, there are few real dissidents.