Francisco de Asís León Bogislao de Greiff Haeusler (July 22, 1895 – July 11, 1976), was a Colombian poet known for his stylistic innovations and deliberately eclectic use of obscure lexicon. Best known simply as León de Greiff, he often used different pen names. The most popular were Leo le Gris and Gaspar de Nuit. De Greiff was one of the founders of Los Panidas, a literary and artistic group established in 1915 in the city of Medellín. It was a precursor of the modernismo movement in Colombia.