Niwa Nagahide (丹羽長秀; October 16, 1535-May 15, 1585) is a retainer of Oda clan and a daimyo.

From youth, Nagahide served Oda Nobunaga and fought in such battles as battle of Nagashino being one of the most trusted retainer. He was also an effective governor tasked with construction of Azuchi Castle among many of his deeds. The extent of Nobunaga's trust can be seen by the fact that Nagahide married Nobunaga's adopted daughter and his son, Niwa Nagashige married the fourth daughter of Nobunaga.

These services let Nagahide rule over Wakasa Province and Sawayama Castle in Omi Province. On 1581, in a military parade held at Kyoto before eyes of the Emperor as well as foreign missionaries, Nagahide was honored to lead the procession.

On 1582, as Oda Nobutaka's second in command, Nobunaga had Nagahide launch a campaign of Shikoku but before he makes any progress, Nobunaga is killed by Akechi Mitsuhide. Nagahide abandoned the campaign and turned back to help Hashiba Hideyoshi avenge by killing Mitsuhide. At the meeting in Kiyosu Castle where the future of Oda clan was discussed, Nagahide supported Hideyoshi's position and gained Echizen Province and Kaga Province to rule over 1,230,000 koku becoming one of the most powerful retainer and daimyo. However, Nagahide passed away of illness in 1585 without making any impact at all. There is a conflicting record that Nagahide had not died of an illness, but on seeing Hideyoshi gather more power and to eclipse the Oda clan Nagahide had so long served, he felt that he had not lived up for the good of Nobunaga and Oda clan as whole and committed a suicide.