Louis Frank (Brussels, January 22, 1864 - Brussels, July 25, 1917 ) was a Belgian lawyer, philosopher and pioneer of the Belgian feminist movement. As a liberal activist and academician, he devoted his career to the promotion of the rights of women and children and for a new social order. He represented Marie Popelin at the bar during the “Popelin affair” and co-founded the Belgian League for the Rights of Women. At the end of his life, he led a fight for pacifism and campaigned to make the city of Brussels a “federal district of the world”.