The 24-year-old beat GB team-mate Alfie Hewett 6-2 6-1 in 54 minutes to collect his second medal in Rio.
On Thursday, Reid and Hewett had to settle for silver in the doubles event, losing out to French pair Stephane Houdet and Nicolas Peifer.
Reid won the inaugural singles title at Wimbledon this year as well as the Australian Open title.
"I felt I hadn't played that well on the big stage until Australia this year and ever since then I've enjoyed every match on the big stage," said Reid after his latest triumph.
"I was nice and relaxed and managed to play one of the best matches of my life.
"Me and Alfie know each other inside out. We train together, we play doubles together. It just felt like anything I tried tonight came off.
"It's an incredible feeling. I'm really clear headed at the moment but I might just lose the plot as soon as I get back to the locker room."
Scotland's Gordon Reid won Paralympics gold in the wheelchair tennis singles final.