Legal aid is the provision of assistance to people who are unable to afford legal representation and access to the court system. Legal aid is regarded as central in providing access to justice by ensuring equality before the law, the right to counsel and the right to a fair trial. This article describes the development of legal aid and its principles, primarily as known in Europe, the Commonwealth of Nations and in the United States.

Legal aid is essential to guaranteeing equal access to justice for all, as provided for by Article 6.3 of the European Convention on Human Rights regarding criminal law cases and Article 6.1 of the same Convention both for civil and criminal cases. Especially for citizens who do not have sufficient financial means, the provision of legal aid to clients by governments increases the likelihood, within court proceedings, of being assisted by legal professionals for free or at a lower cost, or of receiving financial aid.

A number of delivery models for legal aid have emerged, including duty lawyers, community legal clinics, and the payment of lawyers to deal with cases for individuals who are entitled to legal aid. More informal or general legal advice and assistance may also be provided for free or at low cost through such means as law centres (UK), community legal centres (Australia) or a variety of other organisations which provide various forms of legal aid in and outside of court.