Nitta Yoshioki (新田義興) (died 1358) was a samurai of the Nitta family, who fought for the Imperial Southern Court in the Nanboku-cho period of Japanese history. He was the second son of Nitta Yoshisada.
Yoshioki aided in the 1333 siege of Kamakura, and battled alongside Kitabatake Akiie. The following year, he fought with Kitabatake Akinobu, fortifying Mt. Otoko, but being soon routed from there and forced to seek refuge at Mt. Yoshino.
The conflict with the Ashikaga clan continued for several decades, and in 1352, Yoshioki ousted Ashikaga Motouji from Kamakura, with the aid of his brother Nitta Yoshimune and cousin Wakiya Yoshiharu. Soon after taking control of the city, however, he was forced out by Ashikaga Takauji.
Returning to the countryside of Kozuke and Musashi provinces, Yoshioki continued to fight for some time before being captured by Takezawa Nagahira. He was sentenced to death by the minister of Motouji, Hatakeyama Kunikiyo, and drowned in the Rokugō-gawa. A shrine stands at Yaguchi no watari, the site of his death, and he is revered under the name Nitta-daimyōjin (新田大明神).