Matti Haapoja (September 16, 1845 in Isokyrö – January 8, 1895 in Turku) was a Finnish serial killer who was much covered by the press at the time of the murders.
The exact number of his victims is unknown.
He was convicted of two murders and was scheduled for a trial for his third murder trial when he committed suicide in his cell.
He can be linked to seven other identified murder cases, but most of those happened during his exile in Siberia and are poorly documented, so his involvement is not certain.
It is claimed that he confessed to 18 murders, but there are no details about this supposed confession, and the figure should be regarded as unreliable.
Some sources estimate his total number of murders as 22–25.
He also non-fatally wounded at least six men in knife fights.