Abstract: A mast boot includes a flexible cover for encircling a mast mounted in a mast collar in a deck opening on a sailboat having a lower edge to be positioned around the mast collar and an upper edge to be positioned around the mast above the mast collar and opposing side edges provided with fastener strips therealong for continuously securing the side edges together to position the upper and lower edges tightly against the mast and the mast collar, respectively. Upper and lower clamps for sealing the upper and lower edges include bands to be tightened around the mast to compress the upper and lower edges, respectively, against the mast and the mast collar. Upper and lower edge seals positionable to encircle the mast include strips having fasteners thereon permitting the strips to be positioned to cover the upper and lower clamps, respectively.