This is western trillium (Trillium ovatum), a perennial herb in the lily family. I stumbled upon these early blossoms on a glorious nature walk the other day. Bright splashes of white in a backdrop of muted early spring colours, they are.
In some regions of Canada certain members of Trillium are protected, as picking the flower kills the entire plant. Their fruits are also covered in a fragrant oil used to attract ants for seed dispersal.