Abstract: A modular folding seat for use in vehicles is provided. The seat includes a base securable to the vehicle; a backrest pivotally connected to the base, and can include a removable backrest panel mounted to the backrest. The base or the backrest includes a pair of outwardly extending bosses disposed on opposite sides that are rotatably engageable within recesses disposed in the other one of the base or backrest. The bosses are held within the recesses by a pair of engagement members disposed adjacent or in each recess. The engagement members are capable of being deflected to a non-securing position whereby the bosses can be inserted into or withdrawn from the recesses to assemble or disengage the backrest to or from the base. A plurality of regions of engagement between the base and backrest keep the backrest from over rotating beyond a fully upright position and resist downward folding of the backrest when in the upright position.