The article provides an inventory of diseases affecting olive trees worldwide, caused by viruses, bacteria, and phytoplasma. Fifteen viruses and two bacteria were identified as pathogens on olive trees, with some viruses only found in Europe. The bacteria Pseudomonas savastanoi pv. savastanoi causes olive knot disease, mainly in the Mediterranean region. Xylella fastidiosa is responsible for quick decline syndrome in olive trees, detected in Europe and America. Phytoplasmas were reported in five countries across Europe, Asia, and Australia.