Mianus, formerly Mayamus and Upper Landing, is a neighborhood in the town of Greenwich in the U.S. state of Connecticut. Unlike other Greenwich neighborhoods such as Cos Cob or Old Greenwich, Mianus does not have its own ZIP code or post office. Mianus lies partly in the Cos Cob ZIP code, partly in the Riverside ZIP code area, and partly in the Old Greenwich ZIP code area. It lies at an elevation of 23 feet and is home to an elementary school. Mianus was also home to the Mianus Motor Works, a marine-engine manufacturer.