The southernmost tip of South America, particularly from Argentina (Tierra del Fuego and Cape Horn), is the closest landmass to Antarctica.
- The distance across the Drake Passage from Argentina’s southern tip to the Antarctic Peninsula is about 1000 km (≈ 620 miles).
- This is shorter compared to distances from:
- South Africa (≈ 4000 km),
- Australia (≈ 2600 km),
- New Zealand (≈ 2200 km),
- Brazil (much farther north in South America).
Thus, Argentina is geographically the nearest country to Antarctica.
\fbox{\parbox{0.97\linewidth}{
\centering The closest country to Antarctica is $\boxed{\text{Argentina}}$.
}}