Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section Populus, of the Populus genus.

Populus section Populus, of the Populus (poplar) genus, includes the aspen trees and the white poplar Populus alba. The five typical aspens are all native to cold regions with cool summers, in the north of the Northern Hemisphere, extending south at high altitudes in the mountains. The White Poplar, by contrast, is native to warmer regions, with hot, dry summers. These trees are all medium-sized deciduous trees ranging 15–30 metres (49–98 ft) tall.