Buzbee left the Post in June after she objected to a reorganization plan being put in place by the company's new publisher, Will Lewis, that would have effectively demoted her.
Buzbee, 59, worked for AP for many years and led its global newsroom from 2017 to 2021 before leaving for the Post.
"Her journalistic chops, her management experience, her global understanding and her positive and pragmatic approach are just what we need in this time of upheaval for the world and for the news industry," said Reuters Editor-in-Chief Alessandra Galloni.
Reuters, which is expanding its outreach to consumers with a subscription-based website, newsletter and podcasts, is part of the Toronto-based company Thomson Reuters.