John Denis Teahan (28 August 1900 – 21 October 1968) was an Australian politician who served as a Labor Party member of the Legislative Council of Western Australia from 1954 to 1965, representing North-East Province.
He attended Christian Brothers' College, Kalgoorlie, and then moved to Perth to work as a clerk with the Commonwealth Taxation Office.
Teahan moved back to Kalgoorlie in 1932, setting up as a storekeeper and taxation consultant.
Teahan contested Labor preselection for the 1948 Boulder by-election, but was defeated by Charlie Oliver.
He entered parliament at the 1954 Legislative Council election, defeating Sir Harold Seddon of the Liberal Party (the serving President of the Legislative Council).