Final answer:
The oppressive system in South Africa that legally enforced racial segregation and discrimination against blacks was known as apartheid.
Step-by-step explanation:
The name of the system that oppressed blacks in South Africa is apartheid. Apartheid was a policy of complete separation of racial groups, enforced by law from 1948 until the early 1990s. This system classified South Africans into racial categories: white, black, colored, and Indian/Asian.
Under apartheid, the white minority government imposed legal restrictions on the movements, employment, and social interactions of the black majority, stripping them of civil rights and subjecting them to systematic subjugation and discrimination. The eventual dismantling of apartheid was a complex process that included internal resistance, international pressure, and significant figures such as Nelson Mandela, who led the fight for equality and justice.