Yǔ Xìn 庾信 (513–581), zì Zǐshān 子山, also styled Lánchéng 蘭成, native of Xīnyě 新野 in Nányáng (modern Hénán), was the great bridge poet of the Liáng-Northern-Zhōu transition and the canonical master of medieval Chinese parallel prose (piántǐ wén / sìliù wén 四六文). Son of Yǔ Jiānwú 庾肩吾 (Liáng Sǎnjì chángshì zhōngshūlìng), he served the Liáng Táichéng 臺城 court at Yòuwèi jiāngjūn 右衛將軍, enfeoffed Wǔkāngxiànhóu 武康縣侯. In 554 he was sent on a diplomatic mission to the Western Wèi and held there as a hostage when Hóu Jǐng’s 侯景 rebellion devastated the Liáng south. He never returned. Under Western Wèi he served as Chēqí dàjiāngjūn yí tóng sānsī 車騎大將軍儀同三司; under Northern Zhōu, as Sīzōng zhōngdàifū 司宗中大夫. He retired in early Dàxiàng (579) and died in Kāihuáng 1 (581) just under the Suí.
His work divides into two phases: (a) the elegant gōngtǐ 宮體 fù and shī of the Liáng Táichéng court (paired with Xú Líng 徐陵 as the XúYǔ tǐ 徐庾體); (b) the post-554 Northern phase, the period of his late masterpieces — the Āi Jiāngnán fù 哀江南賦, the Xiǎo yuán fù 小園賦, the Kū shù fù 枯樹賦. Dù Fǔ’s iconic line Yǔ Xìn wén zhāng lǎo gēng chéng 庾信文章老更成 (“Yǔ Xìn’s prose grew finer with age”) canonized the late Yǔ as the formative model of Táng parallel prose. Standard biographies in Zhōushū 41 and Běi shǐ 83. CBDB confirms 513–581.
His writings survive in two annotated editions in the corpus: KR4b0017 Yǔ Kāifǔ jí jiānzhù 庾開府集箋註 (Wú Zhàoyí, Kāngxī era) and KR4b0018 Yǔ Zǐshān jí zhù 庾子山集註 (Ní Fán, 1689; the standard modern reference).