The quake measured 7.5 and struck 77km (48 miles) northwest of the capital Kathmandu, the US Geological Survey said.
There are reports that some buildings have collapsed but there was no initial word on any casualties.
Tremors were felt as far away as the Indian capital Delhi and other cities in northern India, which borders Nepal. Indian authorities are responding.
"We are in the process of finding more information and are working to reach out to those affected, both at home and in Nepal," Prime Minister Narendra Moditweeted.
