Geneviève Bujold was 11 in French Cancan when she played an uncredited character.
That was over 69 years ago in 1955.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 81, and has starred in 69 movies in total, 68 of those since French Cancan was released.
In French Cancan, I think Geneviève Bujold looks: