Stephen Patrick Long (born 13 August 1950) FRS is a British-born American environmental plant physiologist[1] and member of the National Academy of Sciences studying how to improve photosynthesis to increase the yield of food and biofuel crops.

[8] Long has added to our understanding of the long-term impacts of climate change, such as rising levels of carbon dioxide and ozone on plants.

Over his career, Long has worked at Tate & Lyle Ltd. Research Centre, the Smithsonian Institution (1989), the University of Vienna (1989–1990), and Brookhaven National Laboratory (1992–1999).

In 2008, he was named the Edward William and Jane Marr Gutgsell Endowed University Professor of Crop Sciences and Plant Biology.

[13] Long has also served as the director of two ARPA-E-funded projects: Plants Engineered to Replace Oil in Sugarcane and Sweet Sorghum (PETROSS), 2013–2018[14] and Transportation Energy Resource from Renewable Agriculture – Mobile Energy-Crop Phenotyping Platform (TERRA-MEPP), 2015–2019.

"[31] Recent work by Long has centered on how to engineer plants to photosynthesize more efficiently to increase yields of food and bioenergy crops.

Long was instrumental in the development of SoyFACE, the largest open-air laboratory in the word to evaluate the impact of future climatic conditions on crops.

[32] In 2016, he proved that yield could be increased by computer-designed engineering; the results were published in Science,[33] covered by the New York Times,[34] and named one of the top scientific moments of 2016 by the Guardian.

[35] Recently, Long led the team that engineered a crop that needs 25 percent less water—without compromising yield—by altering the expression of one gene that is found in all plants, as reported in Nature Communications.

He has been recognized by Clarivate Analytics (formerly Thomson Reuters) as a highly cited researcher in the field of plant and animal science every year since 2005.