Hornavan, Lake in Arjeplog Municipality, Norrbotten County, Sweden

Hornavan is a lake in Arjeplog Municipality, Swedish Lapland, stretching 70 km northwest from Arjeplog to Jäckvik and containing about 400 islets. Its surface lies 425 m above sea level and fluctuates between 220 and 283 km². The lake reaches a depth of 221 m, making it Sweden's deepest, and its basin bottom still lies 204 m above sea level.

A lake map from the late 19th century already marked deep hollows exceeding 221 metres, though its unclear lettering made it unreliable. On 16 March 2023 SMHI's check soundings showed a flat bottom at about 210 metres, confirming Hornavan as Sweden's deepest lake. The lake has since been regulated for hydroelectric power.

Hornavan holds five native whitefish species: Coregonus pallasii, megalops, maxillaris, nelssonii and widegreni, the last known locally as valaam; a sixth, Coregonus maraena, was introduced in the 1940s. Trolling for trout is also popular. The lake's Pite Sámi name is Tjårvek.

Arjeplog sits on the south-western shore, and the lake stretches 70 km north-west to Jäckvik. The water is drinkable, as in all lakes of the municipality. Because of the subarctic climate the lake freezes over for several months each year despite its depth.

A lake map from the late 1800s already showed depressions deeper than 221 metres, though its labels were hard to read. SMHI's check measurement on 16 March 2023 found a flat bottom at about 210 metres, confirming Hornavan as Sweden's deepest lake. Its basin bottom still lies 204 metres above sea level.