Margaretha "Etha" Tekla Johanna Fles (1857-1948) was a Dutch artist and art critic.

She attended the Rijksakademie van beeldende kunsten (State Academy of Fine Arts) in Amsterdam.

She studied with August Allebé, Adrianus van Everdingen [de], and Anton Mauve.

[3] Fles was a member of Arti et Amicitiae, Nederlandsche Etsclub [nl], the Pulchri Studio, and Vereeniging Voor de Kunst Utrecht.

After leaving Rijksakademie van beeldende kunsten Fles became interested in Impressionism along with the contemporary criticism of William Morris and John Ruskin.