The College alumnus surged clear of fourth in the 200m discipline to claim a maiden Olympic medal with a time of 1:54.72.
Following the race, Greenbank spoke to BBC Sport:
"It is amazing," he said.
"It is a dream come true. I am so happy, over the moon and a bit lost for words, I am not going to lie.
"My first memory of swimming was watching the Beijing Olympics so it has always been an ambition of mine. To come away with a medal, and an individual medal, is absolutely amazing."
Greenbank’s stunning performance can be viewed on the BBC Sport website.
Loughborough’s dedicated 2020 Tokyo Olympic and Paralympic Games website features all the latest news, videos, and medal tables from Japan.