Two ways to measure a border give two different “longest” answers. Canada and the US win on total length. Kazakhstan and Russia win on one unbroken stretch.
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World’s Longest International Borders
Total length, in kilometres
Canada – USA8,891 km — longest overall
Kazakhstan – Russia7,644 km — longest continuous
Chile – Argentina5,308 km
China – India~3,488 km — far shorter
Q79 answer: Canada and the USA share the world’s longest international border by total length — Kazakhstan-Russia wins only on “longest continuous stretch.”
🏛️ Must Know
Two Ways to Measure “Longest”
- Canada-USA: 8,891 km The Canada-United States border is the longest international border in the world by total length — combining 6,416 km with the contiguous US and 2,475 km with Alaska.
- Kazakhstan-Russia: 7,644 km This is the longest continuous (unbroken) international border in the world — second only to Canada-USA’s total, but the longest single stretch.
- The Distinction Matters Canada-US wins on combined total length (two separate border segments); Kazakhstan-Russia wins as one single, unbroken line.
- China-India: ~3,488 km The India-China border (the Line of Actual Control) is far shorter than either of these, and remains disputed in several sectors.
🏘️ Good to Know
Other Notable Borders
- Chile-Argentina At roughly 5,308 km, this is one of the world’s longest borders too, running largely along the Andes mountain range.
- Undefended Border The Canada-US border is famously called the world’s longest “undefended” international border, without permanent military presence along most of it.
- Symbolic Crossing The Peace Arch, straddling this border in British Columbia/Washington state, was built in 1921 to commemorate a century of peace between the two nations.
- Not the Same as Coastline Border length measures land boundary only, distinct from a country’s total coastline length — a common source of confusion in geography questions.
Test Yourself
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📝 Previous Year Question
UPSC CSP 2024 — The World’s Longest Border
- UPSC 2024 The Canada-United States border, at 8,891 km total, is the longest international border in the world by total length — not Chile-Argentina, China-India, or Kazakhstan-Russia (which is longest by continuous stretch alone). See UPSC CSP 2024 GS Paper I, Q79.
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