The NZR A class of 1873 consisted of three types of steam locomotives used on New Zealand's railway network of similar specification but differing detail.

Initially ordered by the Public Works Department for use in the construction of lines in Canterbury and Taranaki, the A class was a small tank locomotive with a wheel arrangement of 0-4-0T.

They were not just used by the Public Works Department; the New Zealand Government Railways also utilised the class to operate revenue services on smaller branch lines.

[4] A further batch was built by Alexander Shanks and Company, of Arbroath, Scotland in 1876 on behalf of the Otago Provincial Council for construction work on the Riverton and Otautau lines in Southland.

When the southern enginemen saw the first A class locomotive arrive for use as a shunter, the name "Dido" was given as a nickname because of its diminutive size.