The Spaniard set up a clash against Marin Cilic next.
In the women's section, the battle between Naomi Osaka and Coco Gauff saw the defending champion sail through.
Here are all the main results.
Nadal thrashed South Korean qualifier Chung Hyeon 6-3, 6-4, 6-2.
A crunch test awaits him in the round of 16 against Cilic.
The Croatian overcame American John Isner 7-5, 3-6, 7-6(6), 6-4.
"I've played quite a few times with Rafa. When you play these top guys you have to come up with your great tennis," said Cilic.
Sixth seed Alexander Zverev fought past Aljaz Bedene 6-7 (4/7), 7-6 (7/4), 6-3, 7-6 (7/3).
The German will now face Diego Schwartzman in the round of 16.
Argentine Schwartzman defeated Tennys Sandgren 6-4, 6-1, 6-3.
Meanwhile, Russia's Andrey Rublev eliminated Nick Kyrgios to qualify for the last 16 with a 7-6 (7/5), 7-6 (7/5), 6-3 win.
This was a blow for the controversial Kyrgios.
Defending champion Osaka overpowered 15-year-old Gauff 6-3, 6-0 in 65 minutes.
15-year-old Gauff was shattered post her loss and this led Osaka to calm her down.
During the on-court interviews, Osaka asked Gauff to join her with the microphone.
"I said no because I knew I was going to cry the whole time, but she encouraged me to do it," said Gauff.
Osaka spoke to Gauff's parents and lauded Coco. "You guys raised an amazing player. I remember I used to see you guys training. Both of us made it and we're still working hard."
This is her best run in a Grand Slam event.
"I think everything is just clicking with me," said Andreescu.
American qualifier Taylor Townsend beat Sorana Cirstea 7-5, 6-2 to continue her magic.
Elsewhere, there were wins for Donna Vekic and Julia Georges.
Love Sports news?
Subscribe to stay updated.