The 51st parallel south is a circle of latitude that is 51 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, the Indian Ocean, the Pacific Ocean and South America.
Starting at the Prime Meridian and heading eastwards, the parallel 51° south passes through:
| Co-ordinates | Country, territory or sea | Notes |
|---|---|---|
| Atlantic Ocean | ||
| Indian Ocean | ||
| Pacific Ocean | Passing just south of Adams Island, Auckland Islands, New Zealand | |
| Chile | Patagonic Archipelago and mainland | |
| Argentina | ||
| Atlantic Ocean | Passing just north of the Jason Islands, Falkland Islands - claimed by Argentina |
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