Jōyū 成雄 (also read Seiyū; fl. late 14th to early 15th c.) was a Japanese Shingon disciple of Yūkai 宥快 (1345–1416) on Kōyasan, in the Chū’in-ryū 中院流 transmission line at Hōshō-in 寶性院. He recorded two principal kuden compendia of Yūkai’s oral teachings: KR6t0211 Chū’in-ryū shì and KR6t0212 Chū’in-ryū daiji kikigaki, both of which together with KR6t0210 Chū’in-ryū shido kuden (Yūkai’s own work) form the principal documentary record of the late-medieval Chū’in-ryū. His precise lifedates are not securely recoverable.
Surviving works in the Kanripo corpus: KR6t0211 Chū’in-ryū-ji; KR6t0212 Chū’in-ryū daiji kikigaki.