Official Language Act or Official Languages Act may refer to:
- one of several acts passed in Sri Lanka, including
- the Official Language Act No. 33 of 1956 (Ceylon), commonly known as the Sinhala Only Act, which replaced English with Sinhala as the official language of the country,
- the Tamil Language (Special Provisions) Act No. 28 of 1958 (Ceylon), which allows Tamil in education, public service entrance exams and administration in the Northern and Eastern provinces,
- the Official Languages Act of 1987 (Sri Lanka) passed to make Tamil an official language of the country, and
- the Official Languages Commission Act No. 18 of 1991 (Sri Lanka) passed to establish the Official Languages Commission of Sri Lanka;
- the Official Languages Act (Canada) passed to enshrine official bilingualism;
- the Official Languages Ordinance passed in Hong Kong in 1974 to bring the English and Chinese languages to equal status as official languages of the territory;
- the Official Languages Act (India) passed in 1963; see Official Languages Act
- the Official Languages Act (Ireland) passed to promote the provision of state services in Irish;
- the Official Languages Act (New Brunswick);
- the Official Languages Act (Northwest Territories); and
- the Official Language Act (Quebec), passed to ensure that French retained its primary status.