The Mäntsälä rebellion (Finnish: Mäntsälän kapina) was a failed coup attempt by the Lapua Movement to overthrow the Finnish government.
On February 27, 1932 some 400 armed members of the Suojeluskunta militia interrupted a meeting of Social Democrats in Mäntsälä with small arms fire. This was a local event organized by the local chapter, but the national organization soon joined in. In the next few days, leading members of the Lapua Movement (Lapuanliike) and hundreds of armed members of Suojeluskunta arrived at Mäntsälä. The former Chief of General Staff, Major General Wallenius also joined the leadership of the rebellion. The men refused to disperse and demanded the cabinet's resignation and a change in political course.
Two days later the cabinet ordered the leaders of the Lapua movement arrested using the Protection of the Republic Act which the movement itself had urged for a year before. Army units began preparing as the Chief of Defence, Lieutenant General Aarne Sihvo was prepared to use force to end the rebellion. Orders were given to reinforce the defence of Helsinki with tanks and artillery in case the situation would escalate. As the tensions grew, so did the consumption of alcohol among the instigators.