Aleixo de Abreu (; Alcáçovas do Alentejo, Portugal, 1568–Lisbon, Portugal, 1630) was a Portuguese physician and tropical pathologist.
He graduated in Medicine from the University of Coimbra. Due to his notable work as a physician, he was sent to Angola, along with Afonso Furtado de Mendonça, to study the maladies, believed to be endogenous to that land, that seemed to be afflicting the Portuguese sailors.