Southdown may refer to:
- Southdown (sheep), a breed of sheep
- Southdown, Harpenden, a region in Harpenden, Hertfordshire, England
- Southdown, New Zealand, a suburb of Auckland
- Southdown Creative, an American film and video production company
- Southdown Motor Services, a former bus company based in Sussex, England
- Southdown Power Station, a power station in Auckland