Viscount Niwa Nagahiro (丹羽長裕, April 17, 1859 – July 29, 1886) was a Bakumatsu period Japanese samurai, and the 11th (and final) daimyō of Nihonmatsu Domain in the Tōhoku region of Japan.

Following the defeat of Nihonmatsu Domain during the Boshin War in 1868, Nagakuni was placed under house arrest in Tokyo by the new Meiji government, which also ordered him to retire.

Nagakuni formally adopted his son-in-law, Nagahiro who then became daimyō, with Nihonmatsu reduced to 50,000 koku in its kokudaka (half of what it had previously held).

When the post of daimyō was abolished, Nagahiro remained as Imperial governor of Nihonmatsu until the abolition of the han system.

He died in 1886 and his birth brother Nagayasu (Uesugi Narinori's 11th son) became the 13th chieftain of the Niwa clan.