2019 Tamil Nadu Legislative Assembly By-election
By-elections to eighteen state assembly constituencies were held in Tamil Nadu on 18 April 2019 together with 2019 Indian general election.
It was considered to be mini-assembly election battle for the power in Tamil Nadu. The ruling government had to prove its majority while the opposition was trying hard to get maximum seats.
There were 22 seats vacant in the Tamil Nadu assembly, By-election took place in two phases and in the first phase for 18 assembly constituencies together with Lok Sabha general election on 18 April 2019 in the state. Remaining 4 assembly constituencies election was held on 19 May. The counting of votes was conducted on 23 May, and on the same day the results were announced.
Then the by-elections for 2 seats Vikravandi and Nanguneri were conducted on 21 October 2019
By-Election Event
Phase 1
Phase 1 By-Elections will be held for 18 vacant assembly constituencies in Tamil Nadu.| By-Election Event | Date |
| Election Date Announcement | 10.03.2019 |
| Last Date for Filling Nominations | 26.03.2019 |
| Scrutiny | 27.03.2019 |
| Withdrawal Last Date | 29.03.2019 |
| Voting | 18.04.2019 |
| Results | 23.05.2019 |
Phase 2
Phase 2 By-Elections will be held for the remaining 4 vacant assembly constituencies in Tamil Nadu.| By-Election Event | Date |
| Election Date Announcement | 09.04.2019 |
| Last Date for Filling Nominations | 29.04.2019 |
| Scrutiny | 30.04.2019 |
| Withdrawal Last Date | 02.05.2019 |
| Voting | 19.05.2019 |
| Results | 23.05.2019 |
Notable Party-wise contesting candidates list
There are 36 candidates from the Recognized State political party, 46 candidates from the other registered regional parties and 187 Independent politicians for of total 269 candidates for the 18 seats by-election officially announced by Tamilnadu election commission.| Party | Seats contested | Seats won | Change |
| All India Anna Dravida Munnetra Kazhagam | 22 | 9 | 12 |
| Dravida Munnetra Kazhagam | 22 | 13 | 12 |
| Amma Makkal Munnetra Kazhagam | 22 | 00 | 00 |
| Makkal Needhi Maiam | 20 | 00 | 00 |
| Naam Tamilar Katchi | 22 | 00 | 00 |
| Independent politician | 22 | 00 | 00 |
Opinion Polls
Pre-Poll
| Date published | Polling agency | Others | Lead | |||
| Date published | Polling agency | NDA-AIADMK | UPA-DMK | AMMK | Others | Lead |
| 8 April 2019 | 8-9 | 8-9 | 0 | 0 | 1 | |
| 8 April 2019 | 1 | 17 | 0 | 0 | 16 |