The name Nankai (which means "South Sea") comes from the company's routes along the Nankaidō, the old highway that ran south from the old capital, Kyoto, along the sea coast.

The Nankai network branches out in a generally southern direction from Namba Station in Osaka.

The Nankai Main Line connects Osaka to Wakayama, with an important spur branching to Kansai International Airport.

Koya, headquarters of the Buddhist Shingon sect and a popular pilgrimage site.

On November 1, 2024, Ministry of Land, Infrastructure, Transport and Tourism (MLIT) approved the merger of Nankai Electric Railway and its subsidiary Semboku Rapid Railway, effective April 1, 2025.