Robert Donald McKenzie (19 March 1865 – 14 May 1928) was an Australian businessman and politician who was a member of the Legislative Council of Western Australia from 1904 to 1916.

He came to Western Australia in 1894, during the gold rush, and opened a general store at Hannans (near Kalgoorlie).

McKenzie later expanded his business, becoming a timber and hardware merchant.

He was re-elected in May 1910, and when Frank Wilson replaced Newton Moore as premier a few months later he was made a minister without portfolio in the new ministry.

Wilson's government was defeated in October 1911, and McKenzie left parliament when his term expired in 1916.