Filé powder is the Louisiana spice made from ground sassafras leaves.
The leaves are dried and finely ground into a greenish powder. In Louisiana cooking, filé is especially associated with Choctaw and other Native American food traditions and with Creole cuisine. It can contribute an earthy flavor and help thicken certain dishes.
Filé powder is famously associated with gumbo, where it may be stirred in after cooking or sprinkled at the table. It is not required in every gumbo recipe: okra or a roux may provide thickening instead, and many cooks use more than one thickener.
Filé is not the same as cayenne, paprika, or mustard powder. Those ingredients provide heat, color, or pungency, whereas filé has a distinctive herbal character. Sassafras roots were historically used in beverages and other preparations, but culinary filé is made from the leaves.