Populus fremontii, the Fremont cottonwood or Alamo cottonwood, is a cottonwood (and thus a poplar) native to riparian zones of the Southwestern United States and far northern Mexico. The tree grows near streams, rivers, springs, wetlands, and well-watered alluvial bottomlands at elevations below 2,000 m (6,600 ft) elevation.

Populus fremontii is a large tree growing from 12 m (39 ft) - 35 m (115 ft) in height with a wide crown, with a trunk up to 1.5 m (4.9 ft) in diameter. The bark is smooth when young, becoming deeply fissured with whitish cracked bark on old trees. The Inflorescence consists of a long drooping catkin, which blooms from March to April. The fruit is a wind dispersed achene, that appears to look like patches of cotton hanging from limbs, thus the name cottonwood. The 3 cm (1.2 in) - 7 cm (2.8 in) long leaves, are cordate (heart-shaped) with an elongate tip, with white veins and coarse crenate teeth along the sides, glabrous to hairy, and often stained with milky resin. Autumn colors occur from October-November, mainly a bright yellow, also orange, rarely red.