Esther de Mézerville Ossaye (29 April 1885 - 1971) was a Guatemalan teacher, feminist, suffragette and activist who worked to help women obtain the vote in Costa Rica.

[4] In 1908, she became the principal of the Escuela Superior de Niñas for seven years and in 1917 was appointed Technical Inspector of Schools for San José.

[7] After the Tinoco dictatorship was toppled, she was appointed as director, in 1922, of the Colegio Superior de Señoritas[3] and the following year joined with Acuña in founding the Liga Feminista Costarricense (LFC), first feminist organization in Costa Rica.

[1] De Mezerville resigned the post as school director in 1926 and embarked on a European and North African tour including Algeria, French Morocco, France, Italy and Spain.

In the 1940s, she worked with the Anti-Nazi National Front and was a delegate to the Inter-American Peace conference held in Chapultepec, Mexico City in 1945.