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 .
91²Ö¿â’s dedicated 2020 Tokyo Olympic and Paralympic Games website features all the latest news, videos, and medal tables from Japan.