Zygo Corporation, or simply Zygo, is a manufacturer headquartered at Middlefield, Connecticut that specializes in optical systems and equipment. Their metrology product lines include 3D measuring microscopes using coherence scanning interferometry, laser Fizeau interferometers for testing optical components, laser displacement interferometers, and heterodyne optical encoders for stage position metrology. Zygo’s optics business manufactures both optical assembly and custom optics for medical instruments and national labs. Over 750 patents have been awarded since the Company's founding.

In October 2008, competitor ESI attempted to acquire Zygo for approximately 174 million USD worth of stock but the buy-out was stymied by Zygo's board of directors. Zygo later became part of the Ultra Precision Technologies Division of Ametek, Inc. as a result of a 2014 acquisition.