Su Tseng-chang (蘇貞昌, pinyin: Sū Zhēngchāng) (born July 28, 1947) is the Secretary-General to the President of the Republic of China and one of the founding members of the Democratic Progressive Party.

Born in Pingtung, Su was a practicing lawyer (1973-1983) educated in the National Taiwan University. He was a defense lawyer in the Kaohsiung Incident trials.

He was previously the magistrate of Pingtung County (1989-1994) and magistrate of Taipei County (1997-2004). His first election as the Taipei magistrate was aided by a split between the New Party and the Kuomintang. His subsequent reelection occurred by a wide margin despite the ability of the pan-blue coalition to present a united candidate.

He became Secretary-General to the President when Chen Shui-bian was sworn into his second term in May 2004.

Su is married to Chan Hsiu-ling (詹秀齡 Zhān Xìulíng) with three daughters.

See also: Politics of Taiwan