Abstract: A waste bag for collecting solid waste excretions of a horse includes a bottom cup-like portion and a back portion extending upwardly from the rearward side of the bottom portion. Edges of the back portion are resiliently reinforced so that the back portion conforms to the horse's hips and permits excreted waste to be directed into the bottom portion. A zipper in the bottom portion permits the bag to be selectively emptied without removing the bag from the horse. Drainage holes in the bottom portion automatically drain liquid therefrom. The bag is secured in place by adjustable straps extending from the bag to engage a waistband on the horse.