The insider's guide, from travelers who've actually been through.
Gimpo International Airport (GMP) sits in western Seoul, only about 15 km from the city center, which makes it dramatically closer and quicker to reach than Incheon. It is primarily a domestic hub, with Jeju, Busan, and other Korean cities accounting for most flights, plus a handful of short-haul international routes to Japan, China, and Taiwan. It has two terminals, a larger Domestic Terminal and a smaller, calmer International Terminal, set about 500 meters apart and linked by a covered walkway and free shuttle.
Most of these reach central Seoul in under 30 minutes, with trains every 10 minutes or so.
Gimpo is easy and pleasant to move through, with the International Terminal in particular being quiet and quick to clear. You will find Korean and international food, convenience stores, cafes, lounges, and free wifi. There is also a Lotte Mall connected on the lower level, which is a nice place to pass time.
Because the domestic and international terminals are separate buildings, allow time to move between them via the walkway or shuttle if your connection crosses over. Given how close Gimpo is to Seoul and how fast the subway is, a longer layover here is genuinely worth leaving the airport for.
Use the tools above to check whether your layover is long enough to leave, and how the transit, immigration, and security timings add up for GMP.