The Official Language Act (No. 33 of 1956), commonly referred to as the Sinhala Only Act, was an act passed in the Parliament of Ceylon in 1956. The act replaced English with Sinhala as the sole official language of Ceylon, with the exclusion of Tamil from the act.
At the time, Sinhala (also known as Sinhalese) was the language of Ceylon's majority Sinhalese people, who accounted for around 70% of the country's population. Tamil was the first language of Ceylon's three largest minority ethnic groups, the Indian Tamils, Sri Lankan Tamils and Moors, who together accounted for around 29% of the country's population.
The act was controversial as its supporters saw it as an attempt by a community that had just gained independence to distance themselves from their colonial masters, while its opponents viewed it as an attempt by the linguistic majority to oppress and assert dominance on minorities. The Act symbolizes the post-independent Sinhalese majority's determination to assert Ceylon's identity as a Sinhala Buddhist nation state, and for Tamils, it became a symbol of minority oppression and a justification for them to demand a separate nation-state, Tamil Eelam, which was a factor in the emergence of the decades-long Sri Lankan Civil War.
The policy turned out to be "severely discriminatory" and placed the Tamil-speaking population at a "serious disadvantage". As a Sinhalese academic A. M. Navaratna Bandara writes: "The Tamil-speaking people were given no option but to learn the language of the majority if they wanted to get public service employment. [...] A large number of Tamil public servants had to accept compulsory retirement because of their inability to prove proficiency in the official language [....]" It also entailed that a Sinhalese officer working in Tamil areas was exempted from learning Tamil, but a Tamil officer working in even Tamil areas had to learn Sinhala. The effects of these policies were dramatic as shown by the drastic drop of Tamil representation in public sector: "In 1956, 30 percent of the Ceylon administrative service, 50 percent of the clerical service, 60 percent of engineers and doctors, and 40 percent of the armed forces were Tamil. By 1970 those numbers had plummeted to 5 percent, 5 percent, 10 percent, and 1 percent, respectively." For much of the 1960s government forms and services were virtually unavailable to Tamils, and this situation only partly improved with later relaxations of the law.