Theodore Oscar Unmack (21 December 1835[1] – 17 September 1919)[2] was a politician in Queensland, Australia.

Unmack was born at Hamburg and arrived in Victoria (Australia) in 1853, where he engaged in mercantile pursuits.

[6] He was a prominent Freemason, and held the position of Provincial Grand Master (T.C.).

On the accession to power of Sir Samuel Griffith, Unmack was appointed Secretary for Railways and Postmaster-General on 12 August 1890; he held those roles until 27 March 1893.

[3][4] Unmack died on 17 September 1919 and was buried in Toowong Cemetery.