Marthe Guillain (1890-1974) was a Belgian painter.
Guillain was born in 1890 in Charleroi, Belgium. She was a student of Henry Leonardus van den Houten. She was married to the painter Médard Maertens. She traveled to Istanbul, Paris, and the Belgian Congo. She was a member of the Salon d'Automne.
Guillain died in 1974 in Watermael-Boitsfort, Belgium. Her work in the collection of the Royal Museums of Fine Arts of Belgium.