An asylum seeker is a person who leaves their country of residence, enters another country and applies for asylum (i.e., international protection) in that other country. An asylum seeker is an immigrant who has been forcibly displaced and might have fled their home country because of war or other factors harming them or their family. If their case is accepted, they become considered a refugee. The terms asylum seeker, refugee and illegal immigrant are often confused.

A person becomes an asylum seeker by making a formal application for the right to remain in another country and keeps that status until the application has been concluded. The relevant immigration authorities of the country of asylum determine whether the asylum seeker will be granted protection and become an officially recognized refugee or whether asylum will be refused and the asylum seeker becomes an illegal immigrant who may be asked to leave the country and may even be deported.

In North American English, the term asylee is also used. An asylee can either be an asylum seeker, as defined above, or a person whose claim for asylum was accepted and asylum was granted. On average, about 1 million people apply for asylum every year.

The asylum seeker may be recognised as a refugee and given refugee status if their circumstances fall into the definition of refugee according to the 1951 Refugee Convention or other refugee laws—such as the European Convention on Human Rights, if asylum is claimed within the European Union. However, signatories to the refugee convention create their own policies for assessing the protection status of asylum seekers, and the proportion of asylum applicants who are accepted or rejected varies each year from country to country.