Rule 23 is no accident. As the founder of the modern Olympic Games at the turn of the 20th century, Pierre de Coubertin got to choose what language they would be in, and he was French. But as the century wore on, and English became more dominant as a common international language, French usage at the Games began to fall by the wayside. This alarmed the French-speaking world and the Francophonie organization, one of whose goals, it says, is to “combat the perverse effects of globalization on languages.”

At each Olympics since Athens in 2004, the group has appointed a person known as le Grand Témoin — the Great Witness — whose job is to make the case for, and keep track of, French usage at the Games. This year’s Grand Témoin is the internationally celebrated jazz saxophonist Manu Dibango of Cameroon. (Ms. Jean, a former governor general of Canada, had the job in London in 2012.) Responsibilities include negotiating with the International Olympic Committee and the host country, closely monitoring the French situation at the Games, and producing a report afterward.

The reports tend to reflect a mixture of hopefulness and dismay.

“In Beijing, all Olympic signage appeared first in French, then English and Chinese,” the Sochi report says, for instance. “In Sochi, the signage addressing the international audience was trilingual, but that addressing the spectators appeared in Russian and English.”

In addition, it pointed out, “the arrival of some new sports to the Olympic program (slopestyle and halfpipe) was not accompanied by a terminology sufficient for these disciplines to be discussed with French terms in the media.”

The Olympics are “obviously a very important showcase,” said Mr. Dibango, who is also serving as a cultural ambassador, performing with Brazilian and French-speaking musicians in Rio as a way to promote the international nature of French.