Portugal have not been in Scotland since losing 56-10 during the 2007 World Cup.
At last year’s World Cup, Portugal drew with a vaunted Georgia side and exited on a high with a 24-23 victory against Fiji, who are Scotland’s first opponents in November.
“Fiji and Portugal both play a fast and open brand of rugby and performed very well in the World Cup,” said head coach Townsend.
“This will be a challenge for our defence but should make for two great games .
“Having South Africa as one of our opponents will make for a special occasion. Taking on the reigning world champions is the ultimate test for any team in rugby right now and that will be a game everyone will be looking forward to.
“Our final game against Australia will round off the month nicely, against a team we have fought out some entertaining and close encounters with over the last few years.”