Mildred Barnes Bliss (September 9, 1879 – January 17, 1969) was an American art collector, philanthropist, and one of the cofounders of the Dumbarton Oaks Research Library and Collection in Washington, D.C. Mildred Barnes Bliss was the principal beneficiary of the estates of her stepsister, Cora Barnes, in 1911, and of her mother, Anna Barnes Bliss, in 1935. This wealth was largely based on Demas Barnes’s investments in The Centaur Company, the manufacturers of the laxative Fletcher’s Castoria, the success of which had made him a wealthy man.