A filter for rainwater harvesting forms part of a rainwater catchment system, and includes a container with a lid on its top end, an opening formed in the lid, and a strainer sized and shaped to accommodate the edge of the lid that defines the opening. The strainer includes an upper outwardly directed flange which engages the lid, a vertical side wall that extends downwardly from the upper flange, a lower inwardly directed flange, a reinforcing web supported by the lower flange, a mesh also located above and supported by the lower flange, and a retainer ring located above and supported by the lower flange and adapted to be secured thereto to removably hold the mesh and the reinforcing web therebetween. When the strainer is placed within the opening in the lid and the container is located such that the opening is in the flow path of a rainwater downspout, the strainer allows the passage therethrough of rainwater and filters debris from the rainwater to thereby enable the rainwater to be harvested.