Clara Henriette Hasse (1880 - October 10, 1926) was an American botanist whose research focused on plant pathology. After graduating from the University of Michigan in 1903, she went to Washington, DC to take up an appointment as assistant horticulturist and botanist in the Bureau of Plant Industry at the US Department of Agriculture. Her paper "Pseudomonas citri, the cause of Citrus canker", published in the Journal of Agricultural Research in 1915, was the first to identify the cause of citrus canker and led to the development of methods for controlling the disease which saved the citrus crops in Florida, Alabama, Texas and Mississippi from being wiped out. She died in 1926 at the age of 46.