Francium was discovered in 1939 by the Frenchwoman Marguerite Perey, who established the presence of a 21-minute radio-isotope with properties of an heavy alkali element among the decay products of actinium. Mlle. Perey also isolated this product, determined its radio-chemical and nuclear properties, and showed that actinium is a product of radioactive decay.

The initial proposed name was "actinium K", following the naming system for natural radioactive sources. Later, she proposed the name francium in honor of her country - France.

With the exception of some transuranians, francium is the most unstable element known. Its chemistry is not well known but we can say that it is similar to the other heavier elements of the family such as rubidium and cesium.