Watson Elkinah Reid (1858–1944) was a Canadian architect, a one time member of the California architectural firm, Reid & Reid.
Youngest of three sons who all followed the same profession, he was born in Harvey, New Brunswick to William J. Reid and Lucinda Robinson. He studied at Mount Allison University and about 1888, he joined his brothers James W. and Merritt in California, where he ran their San Diego office, overseeing construction of the massive Hotel del Coronado to his brother's designs. He returned to Canada in 1899 and had a few commissions there under the auspices of Senator Abner Reid McClelan. These included the Riverside-Albert Consolidated School and the Albert County Court House. In his later years he moved to Vancouver where he died.
In 1890, he married Janie R. Turner of Harvey. They had five children, all born before 1901.