The 2015 Taiwanese legislative by-elections were held on 7 February 2015 in Taiwan to elect 5 of the 113 members of the Legislative Yuan for the remaining term until 2016. No change in the party composition of the Legislative Yuan resulted from the by-elections; three Democratic Progressive Party candidates won the seats vacated by DPP legislators, and two Kuomintang candidates won the seats vacated by KMT legislators.
The by-election was the result of resignations by Kuomintang legislator Hsu Yao-chang from Miaoli County's 2nd district; Lin Chia-lung, Democratic Progressive Party legislator for Taichung City's 6th district; Wei Ming-ku, Democratic Progressive Party legislator for Changhua County's 4th district; Lin Ming-chen, Kuomintang legislator for Nantou County's 2nd district; and Pan Men-an, Democratic Progressive Party legislator for Pingtung County's 3rd district.
Hsu Yao-chang, Wei Ming-ku, Lin Ming-chen, and Pan Men-an won their elections for county magistrate, and Lin Chia-lung won his election for mayor in the 2014 local election. Under the Article 73 of the , if any positions become vacant due to resignation or election to another office, and the vacated term is longer than one year, a by-election shall be completed within three months commencing from the date of resignation.
On 5 December 2014, the Central Election Commission announced that by-elections for Taichung 6 and Changhua 4 were to be held on 7 February 2015. Candidate registrations for the two seats were open from 22 to 26 December 2014. On 26 December 2014, the CEC announced that the by-elections for Miaoli 2, Nantou 2, and Pingtung 3 were to be held on 7 February 2015 as well. Candidate registrations for these three seats were open from 26 December 2014 to 9 January 2015.
By-election for Miaoli 2 constituency took place on 7 February 2015. Kuomintang called in head of Gongguan Township to contest the seat. Democratic Progressive Party called in legislator Wu Yi-chen to contest the seat. The DPP originally supported Sunflower Student Movement activist 's bid, but Chen dropped out after allegations of sexual harassment against him surfaced online.
By-election for Taichung 6 constituency took place on 7 February 2015. KMT called in Deputy Secretary-General of the Executive Yuan Hsiao Chia-chi to contest the seat. DPP called in Taichung City councillor Huang Kuo-shu to contest the seat.
By-election for Changhua 4 constituency took place on 7 February 2015. KMT called in former Changhua County magistrate Cho Po-yuan to contest the seat. DPP called in Changhua County councillor Chen Su-yueh to contest the seat. Former Changhua County councillor Hung Li-na announced her bid as an independent after leaving the KMT.
By-election for Nantou 2 constituency took place on 7 February 2015. KMT called in Nantou City mayor Hsu Shu-hua to contest the seat. DPP called in former legislator Tang Huo-shen to contest the seat. Former legislator Chen Cheng-sheng of the People First Party had previously announced his intention to run, but Chen dropped out and supported Tang as the opposition candidate. Assistant professor Shih Chin-fang announced his bid as an independent after leaving the KMT.
By-election for Pingtung 3 constituency took place on 7 February 2015. KMT's nomination shortlist included legislator Su Ching-chuan, former legislator , and Director-General of the Pingtung County Farmer Association Huang Jui-chi. The KMT ultimately called in Liao to contest the seat. DPP called in former Taipei City councillor Liao Wan-ju to contest the seat. Former Executive Yuan advisor had also expressed interest in running, but the DPP nominated Liao after comparing results from hypothetical head-to-head polling.