Start with the dollar bill face up. Fold lengthwise, crease, and unfold. Fold at the center, crease, and unfold.
Fold the left side from the bottom corner, and bring it to the center crease. Fold the right side from the top corner, and bring it to the center crease.
Flip the dollar bill over. Fold the top protruding edge along the top of the dollar bill, and tuck the edge underneath the upper layer. Repeat for the bottom protruding edge of the dollar bill.
Flip the dollar bill again. Fold the bill at the center, and bring the right half over to the left side.
Rotate the dollar bill clockwise 90 degrees. Fold the right and left sides at a 45 degree angle to the bottom of the bill. Let the sides pop back up. These folds create the wings of the butterfly.
Flip the dollar bill over, and fold in the middle of center triangle. Crease and unfold. The dollar bill now resembles a butterfly.