再保险是一家保险公司用以保护自己及其它保险公司以承受损失风险的途径。个人及企业通过签订保险契约以得到面对不同风险（如：龙卷风、地震、法律诉讼、疾病或死亡）时的保障。同理，再保险为保险公司提供类同的保护。

Reinsurance is insurance that is purchased by an insurance company (the "ceding company" or "cedent" or "cedant" under the arrangement) from one or more other insurance companies (the "reinsurer") directly or through a broker as a means of risk management, sometimes in practice including tax mitigation and other reasons described below. The ceding company and the reinsurer enter into a reinsurance agreement which details the conditions upon which the reinsurer would pay a share of the claims incurred by the ceding company. The reinsurer is paid a "reinsurance premium" by the ceding company, which issues insurance policies to its own policyholders.