Mathias de l'Obel, Mathias de Lobel or Matthaeus Lobelius was a Flemish physician and plant enthusiast who was born in Lille, Flanders, in what is now Hauts-de-France, France, and died at Highgate, London, England. He studied at the University of Montpellier and practiced medicine in the low countries and England, including positions as personal physicians to two monarchs. A member of the sixteenth-century Flemish School of Botany, he wrote a series of major treatises on plants in both Latin and Dutch. He was the first botanist to appreciate the distinction between monocotyledons and dicotyledons. The Lobelia plant is named after him.

Monocotyledons, commonly referred to as monocots, are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of the major groups into which the flowering plants have traditionally been divided; the rest of the flowering plants have two cotyledons and are classified as dicotyledons, or dicots.