HIAS, founded as the Hebrew Immigrant Aid Society, is an international Jewish humanitarian nonprofit organization that provides services to refugees, asylum seekers, and displaced people. It was established between 1881 and 1903 to help Eastern European Jewish immigrants to the United States escaping antisemitic persecution and violence. In 1975, the State Department asked HIAS to aid in resettling Vietnam refugees. Since that time, the organization has continued to provide support for refugees of all nationalities, religions and ethnic origins.

Working with host communities, HIAS works with refugees, asylum seekers, and other forcibly displaced and stateless persons. HIAS has offices in the United States and across Latin America, Europe, Africa, and the Middle East. Since its inception, HIAS has helped resettle more than 4.5 million people.

According to HIAS, the acronym HIAS was first used as a telegraphic address and eventually became the universally used name of the organization. A 1909 merger with the Hebrew Sheltering Aid Society resulted in the official name Hebrew Sheltering and Immigrant Aid Society, but the organization continued to be generally known as "H.I.A.S." or more usually as "HIAS", which eventually became the official name.

The Hebrew Immigrant Aid Society was established on November 27, 1881, originally to help the large number of Eastern European Jewish immigrants to the United States who had left Europe to escape antisemitic persecution and violence. J. Harwood Menken was its first president. The organization merged with the Hebrew Sheltering House Association, which had been founded in New York earlier that year.

In 1904, HIAS established a formal bureau on Ellis Island, the primary arrival point of European immigrants to the United States at that time.

In March 1909, the Hebrew Immigrant Aid Society merged with the Hebrew Sheltering House Association to form the Hebrew Sheltering and Immigrant Aid Society, which continued to be widely known as HIAS. By 1914, HIAS had branches in Baltimore, Philadelphia, Boston, and an office in Washington, D.C.

In 1891, Jewish residents of Moscow, St. Petersburg, and Kyiv were expelled and many came to America; beginning in 1892, Ellis Island was the point of entry for most of these new arrivals. In the half-century following the establishment of a formal Ellis Island bureau in 1904, HIAS helped more than 100,000 Jewish immigrants who might otherwise have been turned away. They provided translation services, guided immigrants through medical screening and other procedures, argued before the Boards of Special Enquiry to prevent deportations, lent needy Jews the $25 landing fee, and obtained bonds for others guaranteeing their employable status. The Society was active on the island facilitating legal entry, reception, and immediate care for the newly arrived.

HIAS also searched for relatives of detained immigrants in order to secure the necessary affidavits of support to guarantee that the new arrivals would not become public charges. Lack of such affidavits and/or material means impacted a large number of immigrants: of the 900 immigrants detained during one month in 1917, 600 were held because they had neither money nor friends to claim them. Through advertising and other methods, the society was able to locate relatives for the vast majority of detainees, who in a short time were released from Ellis Island.