How do you get master ball in Pokemon gold?

Answer 1

In Pokemon Gold, after the player defeats Team Rocket and obtains a Rainbow Wing, Professor Elm will give the player a Master Ball. The Master Ball has a one hundred percent capture rate.

Answer 2

profesor Elm will give it to you when you have 8 badges and you'll need it to catch ho-ho in Pokemon gold

p.s you don't have to you use it to catch ho-ho