The present invention is a modular handgrip for rifles and other long guns. The handgrip features a base with a locking dovetail rail on a first side and a second opposite side configured to receive a rail. Back strap additions are provided capable of receiving the rail on the body, which are customizable to a user's preferences while fore straps are provided with rails in a similar manner. Also provided is a storage compartment inside the main body, accessible from a bottom of the grip. As such, an organization, such as an armory, can provide a number of customizable options for handgrips while only stocking a basic grip and a number of optional modules at lower unit and storage costs. Of particular note is a modular fore strap design with an integrated trigger guard.