World Metrology Day is an event occurring on 20 May celebrating the International System of Units. The date is the anniversary of the signing of the Metre Convention in 1875. Metrology is the study of measurement. The World Metrology Day project is currently realized jointly by the International Bureau of Weights and Measures and the International Organization of Legal Metrology.

The theme of World Metrology Day 2020 is “Measurements for Global Trade.”