Mitrephora williamsii is a species of plant in the family Annonaceae.

[2] Charles Budd Robinson, the Canadian botanist who first formally described the species, named it after Robert Statham Williams who collected the specimen that Robinson examined.

The leaves are smooth and shiny green on their upper surfaces while their undersides are brown-green and slightly hairy.

Its fragrant flowers are red and yellow and are arranged in cymes opposite the leaves.

Its flowers have 3, oval-shaped sepals, 5-6 millimeters long, that come to a point at their tip.