责任保险（Liability Insurance），或称第三者保险（Third-party insurance），通指承担第三者损失的保险。该损失系因受保人的行为而产生。受损范围通常包括人体受伤（Bodily Injury）及财物损失（Property Damage）。有些责任保险也承担第三者的个人伤害（Personal Injury）。

Liability insurance is a part of the general insurance system of risk financing to protect the purchaser (the "insured") from the risks of liabilities imposed by lawsuits and similar claims. It protects the insured in the event he or she is sued for claims that come within the coverage of the insurance policy. Originally, individuals or companies that faced a common peril, formed a group and created a self-help fund out of which to pay compensation should any member incur loss (in other words, a mutual insurance arrangement). The modern system relies on dedicated carriers, usually for-profit, to offer protection against specified perils in consideration of a premium. Liability insurance is designed to offer specific protection against third party insurance claims, i.e., payment is not typically made to the insured, but rather to someone suffering loss who is not a party to the insurance contract. In general, damage caused intentionally as well as contractual liability are not covered under liability insurance policies. When a claim is made, the insurance carrier has the duty (and right) to defend the insured. The legal costs of a defence normally do not affect policy limits unless the policy expressly states otherwise; this default rule is useful because defence costs tend to soar when cases go to trial.