Elsa Rehmann (April 11, 1886 – May 30, 1946) was an American landscape architect best known for her pioneering ecological approach to garden design.

She and Edith A. Roberts promoted seeking inspiration in plant communities, which Rehmann considered to be the basis for design criteria and translated them into artistic composition.

Having graduated from Barnard College in 1908, Rehmann studied at the Lowthorpe School of Landscape Architecture, Gardening, and Horticulture for Women.

Her first employers were Charles N. Lowrie, who headed the system of parks of Hudson County, and Marian Cruger Coffin, who specialized in stately gardens.

Most of her clients were in Essex County but she also designed gardens in other parts of New Jersey, as well as in Delaware, New England, New York, and Pennsylvania.

Roberts was developing an outdoor botanical laboratory for the study of plant communities of the Dutchess County, New York, and their biotopes.

Rehmann was asked to interpret the information gathered there from the point of view of an artist, with the intention to show that native plants could be "blended into an attractive landscape picture.