Boat ladders which are at least partly collapsible have been proposed, for example, in U.S. Pat. No. 3,590,952. One advantage of a collapsible boat ladder is that in its collapsed condition it occupies less space which facilitates storage and shipment of the ladder. It is also desirable if the length of the ladder can be adjusted. Foldable ladders have been proposed in U.S. Pat. Nos. 1,603,638, 2,758,770, and 3,286,789. However, the construction of such ladders has been unduly complicated.