☰A risk retention group is a specific kind of member-owned liability insurer created by the federal Liability Risk Retention Act of 1986. A captive is a broader category of owner-insured company chartered under state captive laws. The practical differences are scope and reach.
An RRG may write only liability coverage, never workers compensation or property, and must be owned by the insureds it covers. In exchange, one state license lets it operate in all 50 states through registration, which is why RRGs suit homogeneous groups such as physicians or transportation fleets that need multistate liability coverage without fronting.
A captive can insure nearly any line, including property and workers compensation through a fronting insurer, and it can serve a single owner or a group, but writing admitted coverage across states requires that fronting arrangement. Most RRGs are themselves organized as captives, so the structures are cousins rather than rivals.