The NZR WD class was a class of tank locomotive built by Baldwin Locomotive Works to operate on New Zealand's national rail network. Essentially a more advanced version of 1898's WB class, the eighteen members of the WD class were ordered in 1901 and most entered service that year, though three were not introduced until the start of 1902. Based in locations all around the country, from Auckland in the north to Dunedin in the south, the WD class were suitable for a variety of trains from freight to suburban passenger services. Withdrawal of the class began with WD 356 in January 1933, with the final three, 327, 359, and 360, written off in March 1936. A number were not actually scrapped or dumped, but were sold to work on private industrial lines.