The Arboretum at Flagstaff, Research botanical garden in Flagstaff, Arizona, United States.

The Arboretum at Flagstaff is a 200-acre botanical garden on Woody Mountain Road, 3.8 miles south of Route 66, at 7,150 feet elevation. It grows 750 species of drought-tolerant native and adapted plants from the Colorado Plateau, including a regional Penstemon collection. The site also houses the Merriam-Powell Research Station and the Southwest Experimental Garden Array.

The center was established in 1981 to promote understanding and conservation of plants native to the Colorado Plateau. The project grew from a desire to teach visitors about regional plants through environmental education.

The arboretum hosts workshops, raptor shows, picnics, exhibitions, courses, concerts, edible mushroom and plant forays, and plant sales. It also runs a butterfly garden, a greenhouse, a herbarium, a seed bank, and a gift shop, and is a member of the Center for Plant Conservation, conserving 24 rare plant taxa.

The entrance lies on Woody Mountain Road, 3.8 miles south of U.S. Route 66 on Flagstaff's west side; the grounds sit at 7,150 feet, so expect cool air and strong sun. Paths run from open garden beds into wooded sections, and guided tours, workshops and plant sales are scheduled through the season. A greenhouse, butterfly garden and gift shop stand on site.

The grounds are home to over 750 plant species and more than 130 bird species, making it an important observation site for Colorado Plateau diversity. This combination draws both nature watchers and researchers studying the regional ecosystems.