The longest mountain chain is the Mid-Oceanic Ridge, which runs under all 7 oceans and spans from around California to North of Greenland. It is estimated to be 49,700 miles long. The longest above seal level mountain range is the Andes Mountain Range, which runs down the west border of South America. It is estimated to be 4,300 miles long.
Himalayas contains nine of the top ten tallest mountains in the world, including Mt. Everest, the tallest mountain in the world. This makes the Himalayas not only the largest mountain chain in Asia, but also the largest mountain chain in the world. Also, the Himalayas is the longest mountain chain in Asia.