The Wellington City mayoral by-election, 1912 was part of the New Zealand local elections held that same year. In 1911, elections were held for the Mayor of Wellington plus other local government positions. Thomas Wilford, the incumbent Mayor, resigned due to ill health instigating the need for an election. David McLaren was elected to office as the new Mayor of Wellington, beating three other contenders and becoming the city's first Labour Mayor. The polling was conducted using the standard first-past-the-post electoral method.