Abstract: Modular staircases and staircase assemblies comprising components with notches that fit into and interweave with each other. Certain embodiments of modular staircases have at least two webs, wherein the perimeter of each web resembles a staircase with steps. The webs may be coupled together by a plurality of cross-beams. Each of the webs and the cross-beams may have notches that fit into and interweave with each other to form the basic structure of a staircase. The staircase may also be provided with cover pieces to cover the exposed webs and cross beams, and thus, to provide a surface for a user to sit or step on. Embodiments described herein are modular, in that they may be coupled together in various configurations and thus coupled to straight walls, curved walls, or any combination thereof. Additionally, embodiments described herein may be installed in either vinyl liner-type pools or concrete pools.