Rebecca Suzanne Hornbrook (born 1975) is an atmospheric chemist at the National Center for Atmospheric Research (NCAR). She currently holds the position of Project Scientist II  while also belonging to a variety of groups based out of NCAR, UCAR, and NASA. She is notable for her work as one of the leading experts in Volatile organic compounds (VOCs) while possessing an interest in air quality, biosphere-atmosphere interactions, chemical kinetics, and photochemistry.