- Born: 1566
- Died: 1658
- Titles: Izu no kami (伊豆守)
- Childhood Name: Gensabarô (原三郎)
- Japanese: 真田信之 (Sanada Nobuyuki) 
In 1583, the year following the destruction of the Takeda clan and the death of Oda Nobunaga, Nobuyuki's father Masayuki built Ueda castle and gained control of the Chiisagata District. When Tokugawa Ieyasu attacked Ueda in 1585 in an argument about Noda castle, Nobuyuki was active in the defense. Later he served Ieyasu and married Komatsu, the daughter of Honda Tadakatsu, who had been adopted by Ieyasu. Therefore he was officially Ieyasu's son-in-law.
In 1600 on the eve of the Battle of Sekigahara Nobuyuki was ordered by Ieyasu to participate in the attack on Uesugi Kagekatsu of Aizu, as were his father and brother Nobushige. They got as far as Inuyama in Shimotsuke province when they received a summons (dated 7/17) from the group allied with Ishida Mitsunari inviting them to join against Ieyasu. Masayuki immediately withdrew from Ieyasu's army taking Nobushige with him and returned to Ueda via Numata, where Komatsu refused him admittance, but Nobuyuki stayed with Ieyasu, it is said at his father's direction, presumably so that which ever side won the family would be preserved. On 7/ 24 Ieyasu wrote Nobuyuki a letter thanking him for not going with his father and followed it up three days later by a formal letter giving him his father's possessions in the Chiisagata District (the Ueda area).
Nobuyuki went back to Numata, and then was ordered to join Ieyasu's son Hidetada, who left Utsunomiya on 8/24, as he "moved to Chiisagata." (A similar letter to another general said more directly "to chastise Sanada of Shinshû (Shinano).") Though Hidetada had the much larger army, he did not succeed in the attack against Ueda, and after several days went on west, but he (and Nobuyuki) arrived to late to participate in the battle of Sekigahara.
Having won the battle of Sekigahara, Ieyasu could do as he pleased. Nobuyuki was able to intercede on behalf of his father and brother, so their lives were spared, but they were exiled to Kudoyama (九度山) in Mt. Koya in Kii province. They left Ueda castle the end of 1600. Ieyasu had the fortifications of the castle completely destroyed, and it was handed over to Nobuyuki about the middle of 1601.
Nobuyuki built a mansion in the san-no-maru, east of the main previously fortified section of the castle, and went back and forth between Ueda and Numata. He worked on the devolopment of Ueda as a station on the Hokkokudô Highway which linked the Kantô Plain (Edo) with Echigo province.
Nobuyuki kept in touch with his father and brother in Kudoyama, and when his father died in 1611 he consulted with Honda Masanobu about going into mourning publically. Honda wrote back that as his father had died as an exile, he should get permission from the bakufu before going into mourning.
Nobuyuki was summoned to join the campaign against Osaka castle; he sent his two sons to represent the clan. (His brother Nobushige (Yukimura) was prominent on the Osaka side.)
From about 1616 Nobuyuki concentrated on Ueda Castle, leaving his elder son Nobuyoshi (信吉) in charge of Numata castle. In 1622 he was transferred from Ueda (65,000 koku) to Matsuhiro 松代, in Shinano, formerly also called Kaizu (海津) (100,000 koku), though he kept Numata Castle. This was the first change of location for the clan, most of the members of which had been in Chiisagata for untold generations, though many clans had experienced such moves earlier. Many of the samurai stayed in Ueda or came back to Ueda as commoners. Nobuyuki lived till the age of 92 and never retired. His elder son having already died, he was succeeded by his son Nobumasa (信政).
- Nobuyuki used 信之 on his official seal and often for his signature, and the accounts use that. However two documents of 1608, are signed 信幸. This "yuki" 幸 is the same as that of his father Masayuki 昌幸.
- In 1600 Ieyasu promised him his father's lands "in the Chiisagata District," but as he said nothing about Numata it was presumably already legally his.
- Sanada Family Materials
- Ueda Castle (see the Sanada Family Materials)