Interlaken is located at 566 m (1,857 ft) above sea level, between Lake Brienz to the east and Lake Thun to the west on the alluvial land called B?deli. The town takes its name from its geographical position between the lakes (in Latin inter lacus).

The name "Interlaken" literally means "between lakes" in Latin/German, referring to its unique position between Lake Thun (Thunersee) and Lake Brienz (Brienzersee). To the west lies Lake Thun, which is the larger of the two and is famous for its historical castles (like Schloss Thun and Schloss Oberhofen) and its deep blue waters. To the east lies Lake Brienz, which is known for its stunning, milky-turquoise color caused by glacial particles from the surrounding mountains. The two lakes are connected by the River Aare, which flows through the center of the town. Both lakes offer frequent passenger boat cruises, allowing visitors to explore lakeside villages like Iseltwald (on Lake Brienz) or Spiez (on Lake Thun). These twin lakes, framed by the towering peaks of the Eiger, Mönch, and Jungfrau, are what make Interlaken one of the most famous and photogenic alpine destinations in Switzerland.