The People's Democratic Republic of Ethiopia was a socialist state that existed in Ethiopia and present-day Eritrea from 1987 to 1991.

A one-party state, single-party state, one-party system or single-party system is a governance structure in which only a single political party controls the ruling system. All other parties are either outlawed or only enjoy limited and controlled participation in elections. Sometimes the term "de facto one-party state" is used to describe a dominant-party system that, unlike the one-party state, allows democratic multiparty elections, but the existing practices or balance of political power effectively prevent the opposition from winning power.