Topographically, Korea can be divided into eleven geographic regions.

Level land is a rarity in the Northern Interior, a relatively high mountainous region in north central Korea that slopes generally northward and westward. The numerous peaks of the Northern Interior form a steep and rugged landscape that rarely exceeds a height of 1,200 meters (3,937 ft) above sea level. The mountainous interior is an isolated, nearly inaccessible, and sparsely populated part of Korea dominated by the Choguryong, Hamgyong, Kangnam, Machollyong, Myohyang, Myorak, Nangnim, and PujolLyong Mountain Ranges.

The Korean Peninsula is a rather stable land mass despite its proximity to Japan. Although much of the peninsula's rugged, mountainous landscape resulted from volcanic activity in Kore's dim past, the peninsula has neither active volcanoes nor strong earthquakes. Volcanic activity developed several lava plateaus including the Shinge, Koksan, and Chorwon Plateaus. Along Korea's northern border with China sits the Kaema Plateau at an average elevation of 1,500 meters (4,921 ft). Mt. Paektu, Korea's highest peak and the source of the Yalu and Tumen Rivers, dominates the northwestern corner of this lava plateau, an area often called the "roof of Korea." Just north of Mt. Paektu's summit is a large crater lake named Chonji, meaning "Heavenly Lake."

The Tumen River Valley, located in the northeastern-most corner of Korea, is an area of low hills and valleys with several convenient harbors along its coast.

The Northeastern Coastal Hills and Valleys consist of old granite and metamorphic rock with many small streams falling from the escarpment to the sea, forming their own flood and delta plains. Streams usually cut narrow channels with high and vertical walls in these flows due to the columnar joints in the lava, resulting in a picturesque landscape. The coastal valleys are used extensively for irrigated rice fields and fishing villages are located all along the coast.

The mountainous terrain that parallels Korea's east coast drops sharply into the Sea of Japan, leaving a relatively smooth coastline marked by steep sea cliffs and rocky beaches. Between Yonghung Bay in the north and Yongil Bay in the south, many of the small streams that drop from the high terrain into the sea have created coastal lagoons enclosed by sand spits and bars.

Northwestern Korea is a mixture of terrain features. The western part of this region has extensive plains that provide agricultural land along the shallow Yellow Sea. The largest plains in North Korea are the Pyongyang, Unjon, Anju, Chaeryong, Yonbaek, Hamhung, Yongchon, Kilchu, Yonghung, and Susong. The eastern extent of this region is a complex land of high relief that provides considerable mineral resources.

Central Korea, including the lower courses of the Han River and its tributaries, is an area of extensive and fertile plains and rounded hills. In the east are the Diamond Mountains, remarkable for the beautiful rock formations that have resulted from unequal weathering. A large part of the agricultural land of Korea lies in the south and virtually all the long and navigable rivers are in the south. The majority of Korea's harbors are on the Yellow Sea.

The Southeastern Littoral is a series of short valleys and rocky headlands that lie along a narrow strip of Korea's eastern coastline. The Nangnim Mountain Range in the north and the T'aebaek Mountain Range in the south, with its lesser branch, the Sobaek Range running in a northeast-southwest direction, form an east-west division that isolates this region from the rest of the peninsula. Even the valleys have no convenient connections.

Many of Korea's highest summits occur along the Nangnim and T'aebaek Ranges. The peaks form a spectacular panorama of granite pinnacles and deep narrow canyons with many waterfalls and rapids.

The Southern Mountains and Valleys divide the Naktong Basin from those of the Han and Kum Rivers. The parallel mountains on the western slope are mostly a series of continuous high hills, especially toward the west coast, offering no significant barriers to communications between the lowlands. However, the relatively high Sobaek range historically has obstructed free intercourse between the central and the southern regions and also between the eastern and the western districts in the southern region. Mt. Chirisan (1,915m / 6,283 ft) is the highest summit in the range.

The Naktong River Basin is a hilly country with broad flood plains that occupies southeastern Korea. Low hills are predominant in the south and west and gradually yield to higher mountains in the east and north. Korea's western and southern slopes are gradual and meet with plains, low hills, and winding river basins.

The Southern Littoral is formed by the thousands of islands, peninsulas, hills, and very small plains situated in the southwestern part of the peninsula. The west and south coasts have extremely irregular shorelines as the rolling terrain follows the peninsular tilt into the sea. Most of Korea's 3,479 islands are the result of these nearly hidden ridges and mountains. The length of the southern coastline is nearly eight times its straight-line measurement.

The last two topographic regions are formed by volcanic islands:  Cheju-do and Ullung-do.

Cheju Island, located 138 km (86 mi) off Korea's southwest coast, is a product of volcanic activity and has numerous lava tunnels and sea cliffs. Mt. Hallasan (1,950m / 6,398 ft), located in the center of Cheju Island, is the highest mountain in South Korea. The small crater lake Paegnoktam at the summit of Mt. Hallasan has over 360 parasitic cones. The volcano was last active in 1007 AD.

Ullung Island rises steeply from the East Sea, 137 km (86mi) east of Samchok at roughly the same latitude as Seoul. The dormant volcanic peak Songinbong, "Saint's Peak," (986 m / 3,235 ft) dominates this small island. Though the terrain is steep and rocky, Ullungdo is lush during the summer, and its surrounding crystal clear waters are beautiful.