Brash is a surname. Notable people with the surname include:
- Alan Brash (1913–2002), leading minister of the Presbyterian Church of Aotearoa New Zealand
- Alan Brash (pharmacologist) (born 1949), Scottish pharmacologist
- Don Brash (born 1940), former New Zealand politician
- Jonathan Brash, British politician
- Marion Brash (1931–2022), American actress
- Matt Brash (veterinarian), British veterinarian and television presenter
- Matt Brash (baseball), (born 1998), Canadian baseball player
- Peter Brash (born 1954), American television soap opera writer
- Thomas Brash (1874–1957), leading figure in New Zealand's dairy industry
- William W. Brash III, American judge