The oldest winner of The Voice is Linda Ronstadt, who won season 17 at the age of 73. She competed on the show in 2019, making her the oldest contestant to win the show.
Ronstadt's win highlighted the show's diverse range of contestants and its ability to appeal to a wide audience. She was already a celebrated singer with a long and successful career, but her victory on The Voice proved that age is no barrier to success in the music industry.
It is important to note that "oldest" can be interpreted in different ways. For instance, one could also be asking about the oldest contestant ever to appear on The Voice. This information is not readily available, but it is likely that there have been older contestants who did not win the competition.