Lucas Liu Hsien-tang (; born 21 December 1928) is a Taiwanese prelate of the Catholic Church who served as the Bishop of the Diocese of Hsinchu in Taiwan from 1983 to 2004.
Lucas Liu was born on 21 December 1928 in Tung Shung Tan, Xian (present-day Hebei Province, China). He was ordained a priest on 30 November 1956.
On 24 October 1980, Liu was appointed Coadjutor Bishop of Hsinchu, and he received episcopal consecration on 1 January 1981, with Bishop Peter Tou Pao-Zin as principal consecrator. He succeeded Bishop Tou as Bishop of Hsinchu on 29 June 1983.
Liu led the Catholic community of Hsinchu, a diocese in northwestern Taiwan that is part of the ecclesiastical province of Roman Catholic Archdiocese of Taipei. On 4 December 2004, his resignation was accepted by Pope John Paul II upon reaching the customary retirement age for bishops, making him Bishop Emeritus of Hsinchu.
During his tenure, Liu participated in episcopal ministry in Taiwan and co-consecrated John Baptist Lee Keh-mien, later Bishop of Hsinchu.