The accumulation of the required support means that lawmakers must now consider a bill which was previously blocked at the committee stage.
Members of the public rushed to support the “I Do 2013” campaign, which was launched Tuesday to gather the 50,000 signatures required to compel Parliament to consider legalising same-sex marriages.
Public enthusiasm for the petition was so great that the Ministry of Justice's civic proposal website kansalaisaloite.fi crashed as a result of the overwhelming demand.
The drive was launched with the aim of gathering 250,000 signatories. Supporters of the petition believe that marriage should be afforded to all regardless of sexual orientation.
Finland remains the only Nordic country that does not recognise same-sex marriages.
At the end of February, Parliament’s Legal Affairs Committee decided by a narrow vote not to table the bill for discussion and balloting.
By Wednesday morning, more than 107,000 adult Finns had signed the petition. Parliament still has to decide how exactly it will handle citizens' initiatives, after the first one aiming to ban fur farming was presented to MPs earlier this month.