Mianus , formerly Mayamus and Upper Landing, is a neighborhood in the town of Greenwich in 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 (7 m) and is home to an elementary school. Mianus was also home to the Mianus Motor Works, a marine engine manufacturer.
The neighborhood is located north of the dammed section of the Mianus River at East Putnam Avenue. The dam separates the tidal salt water estuary from the fresh water river. The area above the dam is called Mianus Pond.
The area and the river are named after the chief of the Siwanoy Tribe of Native Americans that inhabited the area when Europeans first encountered them. The Siwanoys sold areas of what is now called "Old Greenwich" to the first English settlers of the town for "40 English Coates" in 1640.