Abstract: A catheter (e.g., high-density mapping catheter) and related catheter system is described herein. The catheter includes an elongated catheter shaft, and an electrode assembly. The electrode assembly includes a first spline assembly, a second spline assembly, and a distal coupler assembly. Each of the spline assembly includes a distal portion and spline assembly electrodes distributed along the spline assembly. The distal coupler assembly includes a base member and a distal electrode. The base member defines an opening configured to receive and accommodate the distal portion of the second spline assembly. The distal electrode is configured to be mounted to the base member to secure the distal portion of the second spline assembly within the opening. The distal electrode can be configured for cardiac mapping, tissue ablation, and/or bipolar pacing.