William E. Blackall (1876–1941) was a Western Australia medical doctor who made a substantial contribution to that state's botany.
Born in Folkestone, Kent, England, he emigrated to Perth in 1905.
He also began production of an illustrated key to the flora of Western Australia in the 1920s, but died before it was complete.
His manuscript was neglected until 1947, when his family asked the University of Western Australia to complete it.
This work was taken up by Professor Brian Grieve, and resulted in the well-known series How to know Western Australian wildflowers.