The Z23 class (formerly O.446 class) was a class of steam locomotives built in 1891 for the New South Wales Government Railways in Australia.
Although this may have been the result of a contemporary anti-American bias, these locomotives were said to be too heavy and too wide at the cylinders, and were the subject of a Royal Commission.
2305 was the first withdrawn in May 1933. By 1941, only six were left, with the last, 2304, being withdrawn in September 1946. None has survived onto preservation.