The concept of societal security as developed by the Copenhagen school has three underlying weaknesses: a tendency to reify societies as independent social agents, a use of too vague a definition of ‘identity’, and a failure to demonstrate sufficiently that social security matters to individuals. This article shows that applying social identity theory to the societal security concept helps remedy these weaknesses and closes the theoretical gaps that the Copenhagen school has left open. It enables us to treat ‘society’ as an independent variable without reifying it as an independent agent. It also suggests a much sharper definition of identity, and a rationale for the Copenhagen school's claim that individuals have a psychological need to achieve societal security by protecting their group boundaries. Social identity theory thus supports the societal security concept in its central assumptions while giving it stronger theoretical foundations and greater analytical clout.