- Sinclair, Upton Sinclair, Upton Beall Sinclair - United States writer whose novels argued for social reform (1878-1968)
--1 is a kind of writer, author
- Sinclair, Clive Sinclair, Sir Clive Marles Sinclair - English electrical engineer who founded a company that introduced many innovative products (born in 1940)
--2 is a kind of electrical engineer; entrepreneur, enterpriser