Delphinium trolliifolium is a species of larkspur known by the common names poison delphinium, cow poison, and Columbian larkspur.

It is native to Washington, Oregon, and northern California.

[1] This wildflower reaches one half to just over one meter in height.

It has large, shiny, deeply lobed leaves.

The spur exceeds two centimeters in length in the largest of the flowers.