The Turkish carrier will launch three times weekly flights to the Omani capital on July 3.
This will increase to four times weekly from July 15.
Stansted-Muscat services, via Istanbul, will operate on Tuesdays, Thursdays and Saturdays, returning Wednesdays, Fridays and Sundays.
Prices start from £115.99.
Meanwhile, Pegasus has rolled out daily flights to Saudi Arabia’s third largest city Dammam, via Istanbul, with fares starting from £159.99.
The additions takes Pegasus’s network to 110 destinations in 43 countries.