1870 Boston mayoral election

The Boston mayoral election of 1870 saw the election of Democratic Party nominee William Gaston over Republican Party nominee George O. Carpenter.

Nominees
At the end of November, William Gaston (the former mayor of Roxbury, Massachusetts and a former Democratic state senator) was nominated by a citizen's committee organized by the city's Democratic Party organization. Gaston had, the month prior, unsuccessfully ran for United States Congress as a Democratic nominee in Massachusetts's third congressional district.

George O. Carpenter (a Boston alderman) was formally made the Republican nominee at a citizens meeting held at Faneuil Hall on December 7.

Ahead of the election, the Boston Evening Transcript and others regarded Gaston to be the front-runner Many Republicans organized in citizens committees that instead backed the candidacy of Gaston. Carpenter suffered from a public image that associated him with political corruption during his time as an alderman. Meanwhile, Gaston's past tenure as mayor of Roxbury was well-regarded.