Brazil has agreements with a number of countries to waive visas for short visits. Please check if you need a visa to enter Brazil. You can find out such information from the Ministry for Foreign Affairs of Brazil, availble both in Portuguese and in English at:
https://www.gov.br/mre/pt-br/assuntos/portal-consular/vistos/informacoes-sobre-vistos-para-estrangeiros-viajarem-ao-brasil
If you do need a visa, we recommend that you get in contact with the Brazilian embassy or consulate at your country of residence to verify if there is any specific document you need.
To request a visa support letter from the conference organisation, please fill out the form available at the following link:
