The Municipal Action Group (MAG; French: Groupe d'action municipale) was a municipal political party that existed from 1978 to 1985 in Montreal, Quebec, Canada.
The Municipal Action Group was formed in 1978 as a breakaway from the progressive Montreal Citizens' Movement (MCM), which had become the official opposition on Montreal city council in the 1974 municipal election. The MCM was initially supported by a heterogeneous community that included trade unionists, Parti Québécois and New Democratic Party supporters, and a variety of social activists. The party later became divided between its radical and centrist members, with some of the centrists forming the nucleus of the MAG. Both parties were regarded as being to the left of mayor Jean Drapeau's Civic Party, which dominated city politics in this period.
The MAG's founding members included two sitting councillors who had been elected for the MCM — Nick Auf der Maur and Bob Keaton — and Liberal Member of Parliament (MP) Serge Joyal, who was nominated as the party's candidate for mayor.
Both the MAG and the MCM ran full candidate slates in the 1978 municipal election. The parties initially pledged to run respectful campaigns against one another, and their mayoral candidates speculated about forming a coalition government after the election. By the end of the campaign, however, relations between the parties had broken down into animosity. On election day, the split in the progressive vote resulted in a landslide victory for the Civic Party; Joyal finished a distant second in the mayoral contest, while Auf der Maur was the MAG's only candidate elected to council. The MCM also suffered a serious defeat; Michael Fainstat was the party's only successful candidate for council.