MEA Viewer (Github repository) is a high performance GPU accelerated application for viewing multi-channel electrophysiological data recorded by multi-electrode arrays (MEAs). Typically these data records display 120 channels of data recorded at 20 kHz for 3-5 minutes, resulting in file sizes near 1 GB. MEA Viewer allows for the rapid investigation and comparison of many recorded extracellular signals for unbiased exploratory data investigation. It is written in Python and Cython, using vispy as its main interface to the graphics hardware. MEA Viewer is part of MEA Tools, a wider Python package for interacting with MEA data.