The Declaration on the Essence of Esperantism (Esperanto: Deklaracio pri la esenco de Esperantismo), commonly referred to as the Declaration of Boulogne (Bulonja Deklaracio), is a historic document that establishes several important premises for the Esperanto movement.

[1] The Declaration was written by L. L. Zamenhof and ratified in 1905 by the attendees of the first World Esperanto Congress, held in Boulogne-sur-Mer, France.

[2] The Declaration of Boulogne consists of an introduction and five points.

In the introduction, Zamenhof clarifies that the five points of the Declaration are necessary to establish because many people misunderstand the nature of the Esperanto movement.

The five points are largely in response to these widely held misconceptions.