The Cambridge Certificate in Teaching English to Speakers of Other Languages (CELTA) is the most widely recognized TESL/TEFL certificate in the world. It is an initial certificate, typically for people with their BAs but also for people with advanced degrees that are not English teaching degrees. The CELTA is highly regarded around the world because of its high standards and rigorous assessments.

https://global.utexas.edu/english-language-center/teach-abroad/celta