Paul Daniel Hahn (5 January 1849 – 9 March 1919) was a South African educational chemical analyst and professor of chemistry.

In January 1876 he was appointed the Jamison Professor in Experimental Physics and Practical Chemistry at the South African College, Cape Town.

Prior to this, Hahn had already admitted four women to his chemistry class as a trial trun the preceding year.

In 1894, Hahn and Professor Lewis undertook a successful tour of the Transvaal and Kimberley in order to raise money for a new physics laboratory.

He also campaigned for the development of the state forestry school and the introduction of agricultural education at Victoria College, currently Stellenbosch University.

He encouraged development of the government laboratories in Cape Town and his advice was sought on a wide variety of scientific and scientific-legal problems.

On 28 June 1875, Hahn married Marie Aneck van Gotha and they had six children: three sons and three daughters.