William Morton Purkiss (1844–8 August 1906) was a Member of the Western Australian Legislative Assembly from 1901 to 1904.
On 1 January 1873 he married Julia Emma Hawkins at Hokitika, New Zealand; they had three sons and a daughter.
In 1894, Purkiss emigrated to Perth, Western Australia, where he worked as a solicitor.
On 6 December 1901 he was elected to the Legislative Assembly seat of Perth, defeating Frank Wilson in a ministerial by-election.
Purkiss retired from practice in 1905, and the following January was appointed Judicial Commissioner for the North West.