Red Deer, city (1991 pop. 58,134), S central Alta., Canada, on the Red Deer River. It developed as a trade and service center for a region of dairying and mixed farming. The discovery of oil and natural gas after World War II lead to the growth of Red Deer's petroleum service industry, as well as the steady growth of the city itself. Red Deer is also in the center of a resort area that includes Sylvan Lake and Gaetz Lake.