Proviso means a conditional provision to an agreement. It may refer to Proviso Township, Cook County, Illinois, United States Proviso Township High Schools District 209 that comprises Proviso East High School Proviso West High School Proviso Mathematics and Science Academy Wilmot Proviso, an American law to ban slavery in annexed territory from Mexico proposed by David Wilmot in the 1840s Lockean proviso, a feature of John Locke's labour theory of property