By-elections to the Invercargill City Council occur to fill vacant seats in the City Council. The death, resignation, bankruptcy or expulsion of a sitting councillor can cause a by-election to occur. The most recent by-election in Invercargill was in 2023 triggered by the resignation of councillor Nigel Skelt.

There have also been four mayoral by-elections in 1887, 1938, 1942 and 1993.

William Benjamin Scandrett resigned from the council upon being elected mayor. The resulting by-election was won by Tom O'Byrne.^[1][2]

In 1913 Councillor Robert Galbraith resigned after moving residence to Ashburton.^[3]

Councillor John Archer resigned to move to Wellington.^[6] Edward Sheehan won the by-election on 19 January but was forced to resign due to a contract he neglected to surrender prior to being nominated.^[7][8][9] He was again elected on 23 February.^[10][11]

William Baird's seat on the council lapsed in 1920 triggering a by-election.

Councillor Arthur Geddes resigned due to poor health. The by-election was contested by former councillors Alexander Glass and Tom O'Byrne.^[14][15][16]

Councillor Edward Sheehan died on 21 June 1932.^[17] The resulting by-election was won by William Denham on 18 July.^[18][19]

First term councillor Alfred McCarthy resigned after being appointed as Judge of the Native Land Court for the Cook Islands in February 1939.^[22]

Councillor John Pickard died on 10 January 1949, prompting a by-election which was won by George Agnew.^[24][25] Councillor Agnew would later die suddenly during a council meeting that November.^[26] The council opted to fill the seat via an appointment rather than hold another by-election.^[27]

Councillor Norman Jones resigned after being elected to parliament, prompting a by-election. Jones was replaced on the council by J. B. Munro, whom he defeated at the parliamentary election. There was also another vacancy so the election was for two seats.^[29]

The 2006 by-election was triggered by the resignation of councillor David Carter due to ill health.

The 2012 by-election was triggered following the resignation of Jackie Kruger.

The 2021 by-election was prompted by the resignation of deputy mayor Toni Biddle in October 2020.^[33] On 17 February 2021, broadcaster Marcus Lush was declared to have won in a landslide.^[34]

On the night of 4 May 2023, Invercargill City councillor Nigel Skelt resigned from his position after fellow councillor Ria Bond threatened to resign if Skelt did not resign following allegations of sexual harassment.^[36] On 2 May 2023, Radio New Zealand reported that a female teenage employee at the ILT Stadium Southland had resigned on 17 February 2023 in response to Skelt's remarks about her physical appearance, naked jelly wrestling, and sexual reproduction. The former employee said she was upset by Skelt's remarks and no longer wanted to work alongside Skelt. At the time, Skelt was working as a stadium manager at ILT Stadium Southland. Radio New Zealand also reported that the Mayor of Invercargill Nobby Clark tried to defuse the situation by paying the teenage employee's NZ$3,000 in lost income, offering the employee counseling and work, issuing a warning to Skelt, and negotiating a confidentiality agreement with the employee. The young woman's parent criticised Clark in a letter for allegedly prioritising Skelt and the stadium's reputation over the hurt and damage experienced by the employee. The incident became public knowledge following a Local Government Official Information Meeting Act media request filed on 29 March 2023.^[37]

Bond welcomed Skelt's decision to resign, stating that "no person should be forced to work with someone who has done the things that he's done." The Invercargill City Council stated that Skelt's resignation would trigger a by-election, which was expected to cost approximately NZ$120,000. Invercargill's last by-election was held in 2020–2021 in response to Toni Biddle's resignation.^[36] The by-election campaign launch began on 1 July 2023. The Holy Trinity Church hosted a campaign launch meeting that was attended by seven candidates and 20 members of the public. The campaign launch covered several topics including the Three Waters reform programme, soup kitchens, Invercargill's Splash Palace changing room policy and Mayor Clark's participation in Julian Batchelor's controversial "Stop Co-Governance" meeting. A further ten meetings were scheduled to be held in Invercargill before voting commences on 13 July.^[38]