The Tenryū Hamanako Line (天竜浜名湖線, Tenryū Hamanako-sen), or Tenhama Line (天浜線, Tenhama-sen) for short, is a Japanese railway line in Shizuoka Prefecture, paralleling the north coast of Lake Hamana between Kakegawa Station in Kakegawa and Shinjohara Station in Kosai.

The Japanese National Railways Futamata Line (二俣線, Futamata sen) was built as an alternative route for the Tokaido Main Line and in particular as a backup for the bridge over Lake Hamana, which was considered potentially vulnerable to weather disruption.

Construction work progressed in the opposite direction with the Futamata-Nishi Line (二俣線西, Futamata-Nishi sen) connecting Shinjohara with Mikkabi on December 1, 1936.

Operations of the former Futamata Line were taken over by the third-sector company Tenryū Hamanako Railroad in 1987,[1] the same year Japanese National Railways was privatized.

Thirty-six features of the line (including bridges and station buildings) are registered tangible cultural properties of Japan.