What Is the Longest River in Iceland? Þjórsá

The longest river in Iceland is Þjórsá (Thjorsa), stretching 230 km (143 mi) from the Hofsjökull glacier in the Central Highlands to the Atlantic Ocean via the Ölfusá estuary near Selfoss.

Key Facts

• Source: Hofsjökull ice cap (1,300 m elevation).
• Major tributaries: Tungnaá, Kaldakvísl, Fossá.
• Þjórsárdalur valley: Scenic farming valley with waterfalls (Hjálparfoss, Háifoss—Iceland's 2nd highest at 122 m).
• Hydroelectric: Búrfell, Sultartangi, Hrauneyjafoss stations—major power for Iceland.
• Salmon fishing: Renowned Atlantic salmon river.
• Saga history: Settlement-era farms (Stöng) buried by Hekla 1104 tephra; reconstructed at Þjóðveldisbærinn.

Runner-Up

Jökulsá á Fjöllum (206 km) – Northeast, from Vatnajökull; includes Dettifoss (Europe's most powerful waterfall).

Þjórsá's glacial milk, volcanic valleys, and clean energy epitomize Iceland's fire-and-ice character.