As of Generation IX, 212 Pokemon can learn Growl. Note this number varies by generation; to check availability by a specific generation, use the command /ds# growl, all
in Pokemon Showdown, where #
is replaced by a number.
This total is nearly guaranteed to increase. If I forget to update this after the next generation comes out, please go to Pokemon Showdown and use the command /nds growl, all
for the most up-to-date total.