Alfred Rehder (4 September 1863, Waldenburg, Saxony – 25 July 1949) was a horticulturist and taxonomist who worked at the Arnold Arboretum of Harvard University. Rehder was a newspaper writer from Germany who was originally hired as a laborer at the Arnold Arboretum. His talents for horticultural plant taxonomy were soon recognized, however. Early in his employment he was sent to Europe to purchase books for the library at the Arboretum.