The Seomjin River originates from Palgongsan and flows for 212.3 kilometers before reaching its final destination in Gwangyang, where it enters Gwangyang Bay.

Principal tributaries include the Boseong River and Yocheon stream.

According to legend, a swarm of toads blocked the Japanese army from crossing the Seomjin into northern Jeolla.

In August 2020, consecutive days of heavier-than-usual rainfall caused the river to overflow and a levee on river collapsed, resulting in massive flooding.

Thousands of residents who lived in villages and towns along the river were left homeless as entire communities were submerged by the floodwaters.