Esperanto Internationally
The longest standing international umbrella organisation for Esperantists is UEA (Universala Esperanto Asocio) which has its central office in Rotterdam, The Netherlands.
For young Esperantists (under the age of 30, although those "young of heart" come along to events) there is the world youth organisation TEJO (Tutmonda Esperantista Junulara Organizo).
As well as UEA the organisation SAT (Sennacia Asocio Tutmonda) whose name is translatable roughly as "The Worldwide Association without Nationalities". SAT has been a powerful force for the progress of Esperanto being the author of its definitve dictionary.