Robert Weir PC MC (5 December 1882 – 7 March 1939) was a Canadian politician.

After working in Ontario he moved to Regina, Saskatchewan, where he taught, worked as an actuary, public school inspector, farmer and horse, cattle and hog breeder.

He was appointed to the Cabinet as Minister of Agriculture under Richard Bennett at a time when farmers were faced with the drought known as the "Dust Bowl" as well as the general crisis of the Great Depression which caused wheat prices to collapse from $1.28 to 60 cents a bushel within three years.

Under Weir's tenure, agricultural researchers attempted to teach farmers how to prevent soil drifting that caused the Dust Bowl and initiated a major grasshopper control campaign in 1933 that reduced crop losses.

Weir's Prairie Farm Rehabilitation Administration Act passed in April 1935.