Deep Notch, sometimes West Kill Notch, or Echo Notch, is a mountain pass in Lexington, New York, United States. It divides two Catskill peaks, both subpeaks of high peaks of the range. The narrow groove between the steep, high slopes on either side is traversed by state highway NY 42 and the Shandaken Tunnel, part of the New York City water supply system. It has been called striking and a marvel of grandeur and beauty.