A connector to couple an electrical stimulation lead to a lead extension can include lead terminals and extension connector contacts that interlock with each other. Another connector can include lead terminals and extension connector contacts that form a hook and loop fastener. Yet another connector defines a lumen for receiving a proximal portion of an electrical stimulation lead and a side-loading slit extending along at least a portion of the longitudinal surface of the connector and extending inwardly to the lumen for side-loading the electrical stimulation lead into the lumen through the side-loading slit.
