Robert Thomson Leiper (17 April 1881 – 21 May 1969) FRS CMG was a British parasitologist and helminthologist.

He spent a year at Mason Science College (which later became the University of Birmingham), matriculating in physics, mathematics, English and Latin.

He then entered the University of Glasgow to study medicine, at which he excelled, winning awards such as the John Hunter Medal and the Senior Arnott Prize in the field; graduating in 1904.

Leiper worked at LSHTM from 1905 until his retirement in 1947, during his time there he studied under Professor Arthur Looss at the University of Cairo and took part in the Egyptian Government's helminthological survey in Uganda.

[3] In 1908, Leiper married Ceinwen Saron (died 1966), a dentist; they had one son and two daughters.