Manitoba Maple (Acer negundo), also known as Ash-leaved Maple or (confusingly) Boxelder, is a species of maple, which occurs throughout most of North America.

It is a small, usually fairly short-lived tree that grows up to 10-20 m tall, with a trunk diameter of 30-50 cm, rarely up to 1 m diameter. The shoots are green, often with a whitish to pink or violet wax coating when young. Unlike most other maples (which usually have palmate leaves), it has pinnate leaves with usually five (sometimes three or seven) leaflets, resembling an ash or an elder, hence the two alternative common names; the leaves are 12-25 cm long, with each leaflet 6-10 cm long and 3-7 cm wide. No other maple ever has more than three leaflets. The flowers are small and with no petals, 10-30 together on drooping racemes 10-20 cm long, produced in early spring. The seeds are paired samaras, each seed slender, 1-2 cm long, with a 2-3 cm incurved wing; they are wind-dispersed.

A few botanists treat it in its own distinct genus, as Negundo aceroides, but this is not widely followed.

There are two subspecies:

• The typical subspecies Acer negundo subsp. negundo, with hairless shoots and leaves, in most of its area: southeast British Columbia east to southern Ontario and New Hampshire, and south to eastern Nevada, Arizona, northernmost Mexico and southeast to Florida. Some authors further subdivide subsp. negundo into a number of regional varieties, but these intergrade and their maintenance as distinct taxa is disputed by many.
• The western subspecies Acer negundo subsp. californicum, with pubescent (finely hairy) shoots and leaves; a disjunct population in the Central Valley area of California.

Several birds feed on the seeds, notably the Evening Grosbeak uses them extensively. The Maple Bug (also known as Boxelder bug) lays its eggs on all maples, but on this species for preference.