Who is the youngest and most popular writer?

It is impossible to determine who the youngest and most popular writer is without specifying a time frame and location. There have been many talented and popular writers throughout history, and their age and popularity can vary greatly depending on these factors. For example, at the time of writing, some of the youngest popular writers include:

Amélie Wen Zhao: A Canadian writer who published her first novel, "Blood Heir," at the age of 15 in 2021.

Darcie Little Badger: An American author of Lipan Apache descent, who gained recognition at a young age with her debut novel, "Elatsoe," published in 2020 when she was 20 years old.

R.F. Kuang: An American writer of Singaporean descent, who rose to prominence with her debut fantasy novel, "The Poppy War," published in 2018 when she was 23 years old.

It is important to note that these are just a few examples and there are many other gifted young writers who have gained popularity for their work.