A Commonwealth republic is any one of the 31 sovereign states of the Commonwealth of Nations with a republican form of government. Though they are nearly all former British colonies, in contrast to the 16 Commonwealth realms they are not in a personal union relationship, do not have Elizabeth II as their respective Head of state, nor do they have another monarch as Head of State. Elizabeth II is still the titular Head of the Commonwealth, but does not have any political power within the Commonwealth republics.

Thirty of the republics are former British self-governing colonies that have evolved into republics by various means. In most cases, the countries achieved independence as Commonwealth realms, and later became Commonwealth republics. In some instances, the countries became Commonwealth republics after achieving independence from other former British colonies (as Bangladesh did from Pakistan in 1971). The latest country to become a Commonwealth republic was Mauritius in 1992. The only member not to have been a British colony is Mozambique, which was a Portuguese colony.