Robert Brown FRSE FRS FLS MWS (December 21, 1773 – June 10, 1858) is a Scottish botanist and palaeobotanist who makes important contributions to botany largely through his pioneering use of the microscope.

His contributions include one of the earliest detailed descriptions of the cell nucleus and cytoplasmic streaming; the first observation of Brownian motion; early work on plant pollination and fertilization, including being the first to recognize the fundamental difference between gymnosperms and angiosperms; and some of the earliest studies in palynology.

He also makes numerous contributions to plant taxonomy, including the erection of a number of plant families that are still accepted today; and numerous Australian plant genera and species, the fruit of his exploration of that continent with Matthew Flinders.