| Mount Sibayak | |
| Other Name: | Gunung Sibayak (Indonesian) Deleng Sibayak (Karo) |
| Elevation M: | 2181 |
| Coordinates: | 3.2392°N 98.5056°W |
| Map: | Indonesia Sumatra |
| Last Eruption: | 1881 |
Mount Sibayak (Indonesian: Gunung Sibayak) is a stratovolcano overlooking the town of Berastagi in northern Sumatra, Indonesia. Although its last eruption was more than a century ago, geothermal activity in the form of steam vents and hot springs remains high on and around the volcano. The vents produce crystalline sulfur, which was mined on a small scale in the past. Seepage of sulfurous gases has also caused acidic discolouration of the small crater lake.
Sibayak is a term from the Karo Batak language referring to a founding community. Mount Sibayak is relatively easy to climb and has been a tourist attraction since colonial times.
On July 11, 1979, a Fokker F28 operating under Garuda Airlines crashed in Mount Sibayak.