Also known as: Ise Moritoki (伊勢盛時), Ise Souzui (伊勢宗瑞), Shinkurou (nickname—新九郎), Souunansouzui (Buddhist—早雲庵宗瑞)

Houjou Souun was the founder of the Later Houjou Clan, but he was never known as "Houjou Souun" during his lifetime. His son Houjou Ujitsuna, who succeeded him as clan head, adopted the clan name of Houjou and posthumously named his father Houjou Souun.

Though popularly portrayed as a humble masterless samurai, Souun's father, Ise Morisada, held an important post as an official of the shogunate according to modern-era research. The name of Ise Shinkurou Moritoki appears in written records from 1481, when he was appointed to a company of troops by Ashikaga Yoshihisa. Souun initially served his brother-in-law, Imagawa Yoshitada, and after his death, help his young son Imagawa Ujichika become the next head of the clan. In gratitude, Ujichika gave him Kokokuji Castle and the "uji" character in his name.

Souun took advantage of general unrest in the Eastern Provinces to take Izu Province for himself in 1493 (an event that many scholars mark as the beginning of the Sengoku), then Odawara Castle and Sagami Province in 1495. He died in 1519, leaving his new terrorities and the clan to his son Houjou Ujitsuna.